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4
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CASE
Ureteric stones
Lisa Bibby and Mostafa Sheba
Expert commentary Andrea Lavinio, Andrew Winterbottom,
and Oliver Wiseman
Case history
A 74- year- old male presented with a 2- day history of right loin pain. The pain was of
gradual onset over 24 hours. On presentation, the pain radiated from the right loin to
right groin. It was associated with nausea. He was assessed by the urology team in the
accident and emergency department. Initial investigations included urinalysis which
was positive for blood.
Learning point Presentation, investigation, and management
Ureteric stones are a common cause for emergency presentation to hospital. Urinary stones affect
2– 3% of the population and have a male predominance. The peak age of presentation is between 40
and 60 years in males and the late 20s in females. Once a patient has a urinary stone, they have a 50%
chance of recurrence, of which 10% reoccur within the first year.
While patients can be asymptomatic, the typical presenting history is of loin to groin pain which is
colicky in nature. It is normally of sudden onset. Stones tend to obstruct at the three narrowest points
in the ureter: the pelviureteric junction, the point at which they cross with the iliac vessels near the
pelvic brim, and the vesicoureteric junction (VUJ). Stones at the VUJ can cause storage symptoms
of urinary frequency and urgency, as well as dysuria and strangury. Furthermore, they can cause
pain which radiates to the tip of the penis or vulva. Renal colic associated with a fever or signs of
sepsis should raise alarms for an infected obstructed system, a pyonephrosis, which is a urological
emergency.
Urinalysis is positive for blood (including trace of blood) in 92.9% of patients and hence not all
patients with renal colic will have a haematuria, either visible or non- visible, on presentation.5
Likewise, blood in the urine can be caused by other presentations of the acute abdomen such as
appendicitis or diverticulitis.
In the acute setting, initial management of suspected renal colic aims to control the pain. National
Institute for Health and Care Excellence (NICE) guidance recommends non- steroidal antiinflammatory drugs (NSAIDs) by any route as first- line treatment.6 Diclofenac suppositories are
commonly used as renal colic often presents with vomiting and so an oral route is less effective.
Paracetamol can be offered first line if there is a contraindication to NSAIDs (such as history of asthma,
gastric ulceration with oral use, or proctitis when using suppositories) or as an adjunct to NSAIDs if
pain is not controlled. NSAIDs should be avoided in renal impairment. If the pain is still not sufficiently
controlled or if both paracetamol and NSAIDs are contraindicated, opioids can be considered.
The exact mechanism of action which enables NSAIDs to exert their analgesic effect in renal colic is
unknown. It is thought to be due to the inhibitory effect on the production of prostaglandins, which
leads to a reduction in diuresis, ureteric wall oedema, and ureteric smooth muscle stimulation.
4
1– 3
6,7
8
36 Challenging Concepts in Urological Surgery
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Evidence base NSAIDs
There have been two Cochrane reviews looking at the use of NSAIDs for the management of acute
renal colic. The first was undertaken in 2005 and compared the effectiveness of NSAIDs to opioids
for analgesia. The review included 29 randomized controlled trials which looked at a total of 1613
patients from nine different countries. Both NSAIDs and opioids were found to reduce patientreported pain scores. Ten of 13 studies reported reduced pain scores when treated with NSAIDs
compared to opioids. There was a significant reduction in the need for rescue medication with
treatment (p < 0.00001). Opioids were associated with high rates of vomiting and hence had a greater
side effect risk.
The second Cochrane review was published in 2015. This compared NSAIDs with antispasmodics.
A total of 50 studies were included in the review of which 37 contributed to the meta- analysis. NSAIDs
significantly reduced pain compared to antispasmodics. Pain recurrence within 24 hours had a higher
incidence in those treated with diclofenac compared to piroxicam.
A non- contrast computed tomography (CT) scan of the kidneys, ureters, and bladder
(KUB) was undertaken to investigate the cause of symptoms. It showed a 6 mm right
mid- ureteric calculus with hydroureteronephrosis to that level (Figure 4.1). The blood
results showed a white cell count (WCC) of 13 × 109/ L, C- reactive protein (CRP) level
of 6 mg/ dL, and creatinine level of 68 μmol/ L.
The pain was well controlled with diclofenac suppositories. The patient was discharged with NSAID analgesia for trial of spontaneous passage and booked for the
stone clinic 2 weeks later. An abdominal X- ray was performed to see if the stone was
visible on X- ray for monitoring purposes. It was not.
9
10
Figure 4.1 A CT KUB scan showing a 6 mm right mid- ureteric stone.
Evidence base The use of CT imaging, ultrasound scanning, and magnetic resonance imaging
https://t.me/med1917
A study of 4000 patients presenting with acute flank pain found a urinary stone on the CT scan of 78%
of patients; 10.5% were found to have an entirely normal CT scan. The alternative diagnoses on the
CT scans of patients presenting with acute flank pain included appendicitis, pancreatitis, renal abscess,
diverticulitis, uterine fibroids, and ovarian masses among many others, including a leaking abdominal
aortic aneurysm.11 Ten per cent of abdominal aortic aneurysms present with symptoms compatible
with renal colic. This is more frequently the case in men over the age of 50 years but also applies to
females.12 These patients tend to present with left- sided pain. CT can also infer a diagnosis of recent
spontaneous passage of a ureteric stone, due to the secondary phenomena of ureteric dilatation and
perinephric stranding or the presence of the stone in the bladder.
13
Non- contrast CT of the abdomen and pelvis (10– 12 mSv) is the gold standard imaging modality for
diagnosis of renal and ureteric stones. NICE guidance recommends this to be undertaken within
the first 24 hours of presentation.
6,14
CT imaging is particularly advantageous as not only can it
identify most ureteric stones, it can provide additional information on size, location, associated
hydronephrosis, fat stranding suggesting inflammation or infection, and the Hounsfield units which
give an indication as to how hard the stone is.
Non- contrast CT has been quoted to have a sensitivity and specificity of 96% and 97% respectively.14
Increasing awareness of exposure to radiation doses has led to the use of low- dose CT (1– 3 mSv). This
has been found to have a high sensitivity and specificity of 97% and 95% respectively.
15
In cases where radiation doses need to be limited, such as in children and younger patients, the use
of ultrasound scanning (USS) as first- line imaging is recommended.6 The benefit of USS is that it does
not use ionizing radiation and is relatively inexpensive. USS can show the secondary features of renal
colic such as hydronephrosis as well as showing some renal stones and VUJ stones in the presence of
a filled bladder. It is less sensitive than CT but has a similar specificity (45% and 94% respectively for
ureteric stones and 45% and 88% for renal stones).16 USS can have limited usefulness in patients with a
high body mass index or in cases where intestinal gas overlies the area of interest.
In pregnant women, NICE guidance advises USS as the first- line imaging technique.6 Renal colic is the
most common non- obstetric cause for abdominal pain in pregnancy. However, USS in pregnancy is
unable to differentiate physiological hydronephrosis from hydronephrosis secondary to an obstructing
ureteric stone. Therefore, USS in pregnancy is reported to have a sensitivity of 34% and specificity of 86%.17
If there is ongoing diagnostic uncertainty, European Association of Urology (EAU) guidance suggests
magnetic resonance imaging as second line and low- dose CT as a last line. Of these three imaging
modalities, CT has the higher positive predictive value (95.8%) compared to magnetic resonance imaging
(80%) and USS (77%) but is last line due to concerns over exposure to ionizing radiation in pregnancy.
18
37Case 4 Ureteric stones
Evidence base Important clinical studies
A large multicentre UK study (Multi- centre cohort study evaluating the role of Inflammatory Markers
In patients presenting with acute ureteric Colic (MIMIC)) was undertaken over 71 hospitals in four
countries. CT images of 4170 patients with acute ureteric colic were reviewed to confirm a single
ureteric stone. The MIMIC study investigated the role of biochemical makers (including creatinine,
CRP, and WCC) in predicting which patients would benefit from intervention and those who
would not. The study was unable to demonstrate a single biomarker which would enable clinicians
to identify patients who would spontaneously pass their stones from those who would require
intervention. It found a spontaneous passage rate of 84% of stones <5 mm in diameter.
Medical expulsion therapy (MET) has been used in the past as it was thought to aid spontaneous
passage of ureteric stones. Its use was recommended in the 2007 joint EAU/ American Urological
Association guideline for the management of ureteral calculi. However, more recently there have been
randomized controlled trials aimed at evaluating the effectiveness of MET.
The Spontaneous Urinary Stone Passage Enabled by Drugs (SUSPEND) study is the largest double- blind,
multicentre randomized controlled trial to date comparing the rate of spontaneous ureteric stone
expulsion in patients treated with tamsulosin, nifedipine, or placebo. This study took data from 24 different
hospitals and included 1136 patients with a CT- proven single ureteric stone. Patients were randomized to
19
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38 Challenging Concepts in Urological Surgery
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daily tamsulosin, nifedipine, or placebo for 4 weeks. Eighty per cent of patients receiving placebo did not
require any further intervention. This compared to 81% of patients taking tamsulosin (p- value 0.73) and
80% of patients taking nifedipine (p- value 0.88). They therefore demonstrated no statistically or clinically
significant difference between the three interventions on rate of spontaneous stone passage.
There has been some criticism of this study. One limiting factor is that the majority of patients had
stones <5 mm which are more likely to be passed spontaneously. Approximately 75% of the patients
had stones <5 mm and 65% were in the lower third of the ureter. The placebo group had a high
rate of no need for further intervention at 80%, which could mask the effects of MET. Furthermore,
the primary endpoint was defined as no need for further intervention rather than CT- proven stone
clearance and so the actual spontaneous passage rate is unknown.
MET was routinely used to aid spontaneous passage of ureteric stones prior to 2015. However,
following the publication of the SUSPEND trial which was unable to demonstrate a significant
difference, this changed. Many clinicians, especially in the UK, have ceased to prescribe MET. Recent
NICE guidance has reviewed all of the evidence surrounding MET including trials more recent than
the SUSPEND trial. It concluded that both calcium channel blockers and alpha blockers can aid the
passage of small stones and be a useful pain management adjunct. Alpha blockers were found to
be more effective than calcium channel blockers and NICE recommends their use for distal ureteric
stones <10 mm. NICE guidance states ‘MET is low cost, and the savings from interventions avoided
because of this therapy, are likely to offset the cost of the therapy’. EAU guidance advises that MET
agents can also reduce the frequency of episodes of colic until stone expulsion.
The patient returned 3 days later to the emergency department with a fever of 38.5°C,
a tachycardia of 120 beats per minute, and blood pressure of 95/ 60 mmHg. His WCC
was 23 × 109/ L, and his CRP level was >250 mg/ dL. The on- call urology team were
called, and the Sepsis Six protocol instituted. A repeat CT KUB scan showed the stone
in the same location as previously, and hydronephrosis and hydroureter above the
stone (Figure 4.2). The team contacted the interventional radiology team for urgent
nephrostomy tube insertion.
21
22
6,18
Figure 4.2 A CT KUB scan showing right hydronephrosis and associated fat stranding.
Expert comment Sepsis
https://t.me/med1917
Urosepsis is defined as ‘life- threatening organ dysfunction caused by a dysregulated host response to
infection of the urinary tract’. Septic shock includes circulatory and metabolic dysfunction and is by
definition associated with significantly higher mortality.23 Urosepsis is estimated to affect >6 million
people worldwide, leading to >1 million deaths globally every year.
Early diagnosis and prompt establishment of treatment are essential. The diagnosis of sepsis is
based on suspicion of infection (i.e. abnormal temperature, leucocytosis, or leucopoenia) and the
presence of organ dysfunction, including (1) abnormal mentation (agitation, drowsiness, confusion
or coma (Glasgow Coma Scale score <15)), (2) increased respiratory rate (≥22 breaths per minute),
and (3) reduced systolic blood pressure (≤100 mmHg). The presence or absence of these three
simple clinical features is used to calculate the quick Sepsis- related Organ Failure Assessment
(qSOFA) and to stratify risk. Mortality is approximately 20% in patients who present with all three
features (qSOFA score of 3). NHS England endorses the latest version of the National Early Warning
Score (NEWS, last updated in 2017) to identify deteriorating patients in a standardized fashion
based on simple physiological parameters. A NEWS score >5 should trigger urgent or emergency
clinical review.
The clinical diagnosis of urinary tract infection can be confirmed by urinalysis demonstrating the
presence of bacteriuria, pyuria, and nitrites in the urine. Bacteriuria and the presence of nitrites
are highly specific but poorly sensitive tests. The absence of pyuria virtually excludes a urinary
tract infection. The most commonly isolated pathogen is Escherichia coli, followed by other
Enterobacteriaceae. Antibiotic- resistant extended spectrum beta- lactamase bacteria are becoming
more prevalent. Inflammatory markers such as CRP and procalcitonin are commonly used to confirm
the diagnosis of sepsis and response to treatment.
Treatment and monitoring should be initiated as soon as possible. The Sepsis Six bundle is designed
to facilitate early intervention with three diagnostic and three therapeutic steps to be delivered within
1 hour (‘golden hour’) to patients with suspected sepsis, irrespective of CRP or procalcitonin values.
The six steps are:
1. Administer oxygen, targeting saturations >94%.
2. Take blood cultures and urinary cultures.
3. Give intravenous antibiotics.
4. Administer intravenous fluids up to 30 mL per kg.
5. Check serial lactates and refer to critical care if lactate >4 mmol/ L.
6. Measure urine output.
If the patient remains hypotensive, drowsy, tachypnoeic or acidotic despite delivering the Sepsis Six
bundle, an urgent referral should be made to critical care outreach.
24
25
39Case 4 Ureteric stones
Evidence base Retrograde ureteric stent versus percutaneous nephrostomy
The infected obstructed kidney is a urological emergency and after urgent decompression carries
a risk of septic shock and mortality. A 2018 study found the risk of septic shock and mortality post
emergency decompression to be 15% and 5% respectively.26 Initial management includes the Sepsis
Six which involves starting empirical antibiotics immediately and fluid resuscitation. EAU guidance
recommends urgent decompression to prevent further complications. Decompression can be
achieved either by cystoscopic insertion of a retrograde ureteric stent or a percutaneous nephrostomy
(PCN). They have been found to be of equal effectiveness with a similar rate of complications. These
patients are often very sick and may require management in an intensive therapy unit (ITU) and so
early involvement with the ITU team is often recommended.
An early randomized controlled study comparing ureteric stents and PCN was undertaken in 1998.
Data were obtained from 42 patients. The time between randomization and intervention was similar
between the two groups. However, procedure time including use of fluoroscopy was less in the
ureteric stent group compared to the PCN group. No statistically significant difference was observed in
length of stay and time for WCC and temperature to normalize. Positive urine cultures were obtained
in 62.9% of patients with a PCN compared to 19.1% of patients with a ureteric stent which was
18
40 Challenging Concepts in Urological Surgery
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statistically significant (p = 0.001). Collection of urine for microscopy and sensitivity testing following
decompression is important for guiding antibiotic treatment. Empirical antibiotics need to be reevaluated as culture results and sensitivities become available. Patients undergoing PCN experienced
greater back pain following the procedure when compared to ureteric stenting (p < 0.05). This
study concluded that the decision between one decompressive intervention over another is based
upon surgeon preference, logistical factors, and stone characteristics. Logistical factors to consider
include the stability of the patient, whether the patient can tolerate lying flat, clotting function and
anticoagulant medications, access to fluoroscopy in emergency theatre, space on emergency theatre
lists, access to interventional radiology, and fitness for anaesthetic.
A more recent retrospective non- randomized study in 2015 looked at 130 patients. Of these patients,
two failed ureteric stent insertion and one failed nephrostomy insertion. The study found patients who
underwent PCN were more likely to have larger stones and be more unwell than patients selected
for ureteric stenting. It found no difference between time from septic event to definitive treatment.
The PCN group had a greater length of stay (p = 0.0001), higher rate of ITU admission (p = 0.006),
and were more unwell than patients selected for ureteric stenting. PCN and ureteric stents were both
found to be equally effective.
Definitive management of the obstructing stone is recommended to be delayed until the sepsis has
resolved and the course of antibiotics has been completed.
Expert comment Percutaneous nephrostomy placement
Expert tip
CT KUB is often performed in a prone position to differentiate between a VUJ stone and a stone that
has passed and sits in the bladder at the VUJ.
Nephrostomy insertion
Indications for nephrostomy insertion include urinary tract obstruction (e.g. stone, tumour, ureteric
stricture, and pregnancy), urine diversion (fistula), and access (percutaneous nephrolithotomy, ureteric
stent, stone retrieval).
Contraindications are few and relative including bleeding disorders, an uncooperative patient,
hyperkalaemia causing cardiac dysfunction, and no percutaneous access to the kidney due to adjacent
organs (e.g. spina bifida).
A nephrostomy is usually performed with the patient lying in a prone position but can also be
performed in a lateral and modified supine position depending on the position of the kidney with
respect to adjacent organs. The procedure is performed as a sterile procedure under local anaesthesia.
Ultrasound is used to guide a needle into the kidney. Access is ideally through the tip of a calyx avoiding
the main blood vessels through Brodel’s avascular plane. Once inside the collecting system, X- rays are
used to monitor a Seldinger technique to place a wire, dilate the tract, and place a pigtail- type drainage
catheter that gets connected to a catheter bag.
Major complications are infrequent, including bleeding (5%), sepsis (1– 3%), and perforation of
adjacent organ (e.g. bowel or pleura) (0.2%).
27
28
18
A nephrostomy tube was inserted and pus was drained. This was sent for culture.
The patient recovered over the next 72 hours, and was discharged on a further course
of oral antibiotics. He was then scheduled to undergo an urgent ureteroscopy (URS)
and laser stone fragmentation.
Evidence base Extracorporeal shock wave lithotripsy and ureteroscopy
https://t.me/med1917
NICE guidance recommends extracorporeal shockwave lithotripsy (ESWL) as first- line treatment of
ureteric stones <10 mm. In cases where ESWL is technically possible, URS can be considered if ESWL
does not clear stones within 4 weeks, previous ESWL courses have failed, the stone cannot be targeted
with ESWL, or there are contraindications to ESWL. The effectiveness of ESWL is affected by the efficiency
of the lithotripter, patient body habitus, the stone itself (size, location, composition), and renal anatomy
(e.g. infundibulopelvic angle, and infundibular length and width of the lower pole calix) which can be
determined radiographically. A wide infundibulopelvic angle or short infundibular length and broad
infundibular width are favourable for stone clearance following ESWL.29 For stones >10 mm, URS is
suggested as first line as the risk of loss of renal function is higher. Percutaneous nephrolithotomy and
antegrade URS can be considered in large proximal impacted stones, especially where URS has failed.
6,18
In situations where there is no pyonephrosis, guidance recommends active treatment of renal colic
within 48 hours of diagnosis or readmission if pain is ongoing and not tolerated or the stone is
unlikely to pass. The rationale behind this is that ureteric colic can be extremely painful and can lead
to loss of renal function.
6
Ureteroscopy has a small benefit over ESWL for stone- free rates, number of repeat treatments
required, and quality of life. However, ESWL offers a shorter hospital stay, associated with less pain
and fewer major adverse effects. ESWL is significantly more cost- effective than URS which is why it is
first line for stones <10 mm. For those larger than 10 mm, URS is recommended due to concerns that
delay in their management can lead to renal obstruction and subsequent permanent damage. This risk
is present with smaller stones but is even greater with stones >10 mm.
6
The patient underwent an elective URS 4 weeks later. At URS, the stone was visualized, and was well fragmented with a holmium laser fibre. All the fragments were
removed with a zero- tip basket and sent for analysis. A JJ stent was placed after the
procedure, and the nephrostomy tube was removed.
41Case 4 Ureteric stones
The patient was consented and marked appropriately. The patient was placed in the
lithotomy position, and was prepped and draped. Intravenous gentamicin and co- amoxiclav
were given in accordance with local antibiotic guidance. A sensor guidewire was passed
up to the right kidney under X- ray guidance. A 7- French (Fr) rigid ureteroscope was passed
alongside the guidewire, and the stone was visualized with some ureteric oedema around
the stone. Irrigation was minimized. A 200 μm holmium laser fibre was passed, and
fragmentation of the stone was commenced. The stone was soft, and was well fragmented
with settings of 0.4 J and 20 Hz. One small piece of stone was seen to remain at the end of
the procedure, and this was grasped with a 1.9 Fr tipless basket, and sent for stone analysis.
A 26 cm, 6 Fr stent was placed. The nephrostomy tube was removed using X- ray control, and
the stent was seen to remain in a good position after nephrostomy tube removal.
Expert comment Operative note
Postoperative plan
The patient was sent home later when able to pass urine. Stent removal in 2 weeks with flexible
cystoscope was planned.
Expert comment Clinical surgical tip
In elderly men, accessing the ureteric orifice (UO) can be difficult, due to the size of the prostate. If
there is a median lobe of the prostate, then entry to the bladder in the groove on the left side should
be undertaken, and the tip of the cystoscope gently pressed down to reveal the UO. It is important to
minimize the number of times the cystoscope comes over the bladder neck, due to increased risk of
contact bleeding which may make the UO harder to find. If the wire which is passed does not come
42 Challenging Concepts in Urological Surgery
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out of the tip of the cystoscope at the 6 o’ clock position, then a retrograde catheter can be placed
through the cystoscope and the wire passed through this. While spending time trying to intubate the
UO, it is important that the surgeon does not overfill the bladder, which may also cause bleeding, and
therefore the irrigation used should be minimized and the bladder should be regularly emptied.
Preventing retropulsion is important when dealing with ureteric stones. While many units do possess
flexible ureteroscopes to retrieve a ureteric stone which has been retropulsed to the kidney, there
are costs associated with this, and the skills and/ or equipment may not always be readily available.
Therefore, minimizing irrigation through the rigid ureteroscope is important. The choice of laser
settings can also help to minimize retropulsion. Settings which involve having a low energy and, if
possible, a longer pulse width will help to do this, as will the use of a smaller (200 μm) laser fibre.
There are a number of anti- retropulsion devices available, but these are not often used unless the
stone is larger and in the upper ureter, in which case some surgeons find them useful.
Fragmentation of a ureteric stone should start at the middle of the stone, to minimize the risk of ureteric
trauma. With a softer stone, the decision to mostly dust the stone will help minimize retropulsion, and
will also mean that there are fewer fragments to remove. It is important to try and have a fragment to
send for analysis if one has not been sent previously, and the fragment must be made small enough
to extract without the risk of traumatizing the ureter or getting the basket stuck with a stone fragment
that is too large. If there is any doubt that the fragment may be too large to extract, it should be further
lasered. If a stone is captured in the basket and then basket extraction becomes difficult because of
a tight ureter, then if a 1.9 Fr basket is used, a 200 μm laser fibre can be passed alongside the basket,
and the stone fragment further lasered to be made small enough to allow removal of the basket.
Occasionally the basket itself may be lasered in this scenario, and if this happens the stone will be
released, making the situation safe, and can then be further lasered to dust, or another basket used to
remove stone fragments once the stone fragment has been further fragmented.
While routine ureteric stenting is not recommended after URS, in this situation, where there was a
history of urosepsis and significant ureteric oedema below the stone, the decision was made to place
a stent for 2 weeks.
Evidence base Ureteric stenting post URS
Routine retrograde ureteric stenting post URS is not recommended after uncomplicated complete stone
removal.18 A review paper looking at ureteric stenting post URS reviewed nine randomized controlled
trials. Patients with stents inserted post URS experienced a higher incidence of lower urinary tract
symptoms such as dysuria, frequency, and urgency than those who had not been stented. No benefit
was elicited in terms of analgesia, urinary tract infections, stone- free rate, or ureteric strictures. However,
ureteric stents did reduce the likelihood of acute admissions to hospital post URS but this difference was
not statistically significant.30 There is a role for ureteric stents post URS in patients who are at increased
risk of complications due to ureteric trauma, residual stone fragments, and bleeding, for example.
The EAU 2019 guidelines18 recommend JJ stent insertion in the following circumstances:
● Ureteric trauma during the procedure.
● Residual stone fragments >2 mm remaining in ureter.
● Bleeding (potential for clot colic).
● Pregnancy.
● If treating an impacted stone (usually ureter very oedematous at site of impaction).
● Prolonged manipulation within ureter, particularly upper one- third.
● After flexible ureteroscopy and use of an access sheath.
● All doubtful cases, to avoid stressful emergencies.
NICE guidance similarly does not recommend routine stenting post URS for stones <20 mm. It
recognized that ureteric stents are associated with numerous adverse effects such as pain, haematuria,
and storage urinary symptoms which impact on quality of life and provide no benefit. Stenting could
be considered where repeat treatment is required, solitary kidney cases, or if there is evidence of
infection or obstruction. No recommendation was made on stones >20 mm because this is a small
group of patients who would undergo variable treatments and the decision to stent would be made
on clinical judgement. There is also a lack of evidence about stenting in this group of patients.
18
6
The patient was reviewed in the outpatient clinic following removal of his stent. He
https://t.me/med1917
was well. The stone was identified as a uric acid stone (94%). The patient underwent
a basic metabolic screen.
Learning point Medical management of stones
EAU guidance advises a biochemical analysis of urine and blood in all patients presenting as an
emergency with renal colic.18 All patients should have a urine dipstick and serum blood samples sent for
creatinine, uric acid, calcium, sodium, potassium, WCC, and CRP (and a clotting screen if intervention
is required). Furthermore, first- time stone formers should have their stones sent for analysis by infrared
spectroscopy or X- ray diffraction. In addition, patients on pharmacological stone prevention, or who
have early or late recurrence following complete stone clearance, should also undergo a stone analysis.
Patients who are managed conservatively are advised to sieve their urine in order to collect the stone
when passed, so that it can be brought to their follow- up clinic and sent for analysis.
Following on from the acute setting, patients are classified as high or low risk for stone recurrence
based on a number of factors including their stone history, the results of the basic blood tests, and
stone analysis performed in the acute setting. Those with risk factors for recurrence are classified as
high risk and therefore require a full metabolic workup at least 20 days after being stone free.
There are many risk factors which increase the risk of stone recurrence. Certain medical conditions
associated with an increased risk include hyperparathyroidism, polycystic kidney disease, and
gastrointestinal diseases such as Crohn’s disease to name but a few. Patients with anatomical
variations of the urinary tract such as ureteral strictures, horseshoe kidneys, and ureteroceles are
also at risk. Furthermore, stone formation in childhood and in teenagers, a family history of stone
formation, and the composition of the stone itself including brushite containing stones, uric acid
stones, and infection stones all increase the risk. A full list of these risk factor can be found in the
EAU guidelines.
Full metabolic testing should consist of one or two 24- hour urine collections obtained on a random
diet and analysed at minimum for total volume, pH, calcium, oxalate, uric acid, citrate, sodium,
potassium, and creatinine.
Due to the high risk of recurrence (approximately 50%), all patients should be counselled on
addressing risk factors. Generic advice includes drinking between 2.5 and 3 L of water daily, eating a
balanced diet with limited salt and animal protein intake, maintaining a heathy body mass index, and
exercising regularly.
Uric acid stones are the only type of stone which can be dissolved by oral alkalinizing agents which
act by raising the urinary pH. Ten per cent of urinary tract stones are composed of uric acid and
are associated with a low urine pH and sometimes hypouricosuria. In patients with a low urinary
pH, oral alkaline citrate such as potassium citrate or sodium bicarbonate can be used to raise the
pH of the urine and dissolve the stone by chemolysis. The target pH is 7.0– 7.2. Patients with uric
acid stones are at high risk of recurrence and can be taught to monitor the pH of their urine with
urine dipsticks and thus adjust the dose of their alkalizing agent according to their urine pH as
prophylaxis.18 No good- quality evidence is available for this therapy, but it has been used for some
time. The principles behind this management and guidance for its clinical use have been provided
by Rodman et al.32 and supported by Becker.33 Monitoring of radiolucent stones during therapy is
usually undertaken by USS, but repeat non- contrast CT might be necessary in some situations.
If they are found to have hyperuricosuria, patients should be treated with allopurinol to reduce the risk
of recurrence.
18
31
18
18
18
32,33
43Case 4 Ureteric stones
A final word from the expert
Ureteric colic is one of the commonest surgical emergencies. It is also one which can present
with a broad range of morbidity, from the patient who has a small stone that has caused
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