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Grade 0 (UTD P1) Grade 1 (UTD P1) Grade 2 (UTD P2) Grade 3 (UTD P3) Grade 4 (UTD P3)
43 Obstructive Uropathy
Table 43.4 Urinary tract dilation (UTD) classication system
Anterior-posterior renal pelvic
diameter (APRPD)
Major calyceal dilation Yes/no
Minor calyceal dilation Yes/no
Parenchymal thickness Normal/abnormal
Parenchymal appearance Normal/abnormal Evaluate for heterogeneity or cysts
Ureters Normal/abnormal
Bladder Normal/abnormal Evaluate for ureteroceles and bladder thickness
Grades UT P1 (low risk) Central calyceal dilation only or low-risk APRPD based on age, normal
Measured at the largest diameter of the renal pelvis
parenchyma/ureters/bladder
UT P2 (intermediate
risk)
UT P3 (high risk) UT P2 with parenchymal or bladder abnormalities
Peripheral calyceal dilation and/or abnormal ureter ± central calyceal dilation ±
intermediate APRPD, normal parenchyma and bladder
479
Fig. 43.1 Depiction of the Society of Fetal Urology grading of hydronephrosis in the sagittal plane. For comparison, the urinary tract dilation
classication system approximate corresponding grade is in parenthesis
appearance can be lost. US can also be useful for detecting
Conventional Therapy
debris, stones, or gas within the renal collecting system.
Evaluation of the ureters on ultrasound can be limited secondary to patient body habitus and bowel gas.
Non-contrast cross-sectional CT imaging has become a
mainstay in the initial evaluation of many abdominal conditions and is excellent at not only assessing for the presence of
Indications for treatment will vary based on the underlying
cause of the hydronephrosis, patient’s symptoms, and extent
of acute renal injury. Conventional therapies for hydronephrosis aim to correct the underlying cause of the
hydronephrosis.
hydronephrosis but very sensitive (97%), specic (96%), and
accurate (97%) for the evaluation of urolithiasis [17]. One
important limitation of CT is the limited ability to detect
Urolithiasis
indinavir and pure matrix stones due to low X-ray beam
attenuation [18, 19]. If the patient’s renal function is adequate to support IV contrast, delayed contrast-enhanced
images (CT urogram) can evaluate the anatomy and patency
of the collecting system, assess urothelial thickness which
can indicate inammation or malignancy, and differentiate
complete from partial obstructions in the setting of
hydronephrosis.
Acute management of a urinary tract stone is based on the
stone’s size, location, presence or absence of associated
hydronephrosis, and extent of renal function loss which is
based on the best practice guidelines of the American Urologic
Association (AUA) [20]. Invasive procedures for stones are
typically performed when the urinary tract is sterile; treat-
ment of any UTI should be attempted prior to intervention.
480
Key Point
Any associated UTI should be treated rst prior to
intervention so as not to disseminate the infection.
Medical therapy generally consists of pain control and
alpha blocker therapy to assist in passing a stone which can
be considered when ureteral stones are less than 10mm or
when there are symptomatic non-obstructing renal pelvis
stones. The time course for spontaneously passing a stone
will vary based on size and location, taking up to 1month for
larger more proximal stones [21]. If a stone fails to pass after
4–6 weeks or if there is clinical decline, more denitive
options may be considered. Active surveillance is recommended with non-obstructing asymptomatic calculi.
Shockwave lithotripsy or ureteroscopic lithotripsy can
be used to treat ureteral stones >10mm, lower pole stone
burden <10mm, or non-lower pole stone burden >20mm.
While ureteroscopy is a more invasive with higher chance
of urothelial injury, it offers a greater chance of stone
removal.
Percutaneous nephrostolithotomy (PCNL) may be offered
for larger kidney stones (>10mm) that would not be adequately treated with lithotripsy and when there is signicant
residual kidney function to justify the procedure. PCNL, as
the name implies, involves using percutaneous access to
place a nephroscope into the collecting system. While PCNL
allows greater visualization of the calyces and a greater
chance of stone removal, there is increased risk of complications including hemorrhage compared with shockwave or
ureteroscopic lithotripsy [20, 22, 23].
Key Point
Percutaneous nephrostolithotomy is indicated for renal
calculi >10mm which could not be adequately treated
with lithotripsy.
Nephrectomy may be offered when there is limited residual kidney function and the affected kidney is causing persistent pain or recurrent infection. Residual kidney function is
typically evaluated with a nuclear medicine scan such as a
MAG3 scan which allows differential of the renal function
per kidney. Contralateral kidney function should be assessed
prior to performing a nephrectomy.
Infection
UTIs without a specic nidus for infection are typically
managed with antibiotics. The most common causative
L. A. Byers and P. J. Rochon
organism is Escherichia coli, and common empiric therapy
includes trimethoprim-sulfamethoxazole (Bactrim) and
nitrofurantoin (Macrobid). A special case to consider is
emphysematous pyelonephritis, which is seen almost
exclusively in diabetics. This was historically treated with a
combination of antibiotics and nephrectomy; however,
more recent research demonstrates signicantly decreased
mortality with a combination of antibiotic therapy and
percutaneous drainage [24].
Key Point
Emphysematous pyelonephritis = Severe infection
with gas forming around the kidney. Treatment
includes antibiotics and percutaneous drainage, rarely
nephrectomy.
BPH
Patients that exhibit uncomplicated LUTS may be managed
medically with alpha blockers, 5-alpha-reductase inhibitors,
and/or anticholinergics. When symptoms become more
bothersome or if complications of BPH (renal injury, recurrent urinary infections, bladder stones, or hematuria) are
present, invasive procedures such as transurethral resection
of the prostate (TURP) or prostatectomy may be considered
[25]. Long-term complications of these procedures include
retrograde ejaculation, erectile dysfunction, and incontinence. An innovative new IR treatment for BPH consists of
prostatic artery embolization (refer to Chap. 29 for more
information).
Urothelial Carcinoma
Treatment will depend on the location of the lesion within
the urinary tract and the depth of invasion. Approximately
90–95% of urothelial cancer will occur in the bladder with
the upper tract lesions occurring in less than 5% of cases;
however, 22–47% of patients with a primary upper tract
lesion will develop a “drop” metastasis to the bladder [26].
For bladder tumors that do not invade the muscularis layer,
local treatment with transurethral resection of bladder tumor
(TURBT) and/or intravesicular instillation of inactivated
mycobacterium bovis (BCG) is the rst line treatment.
Tumors which invade the muscularis may be treated with
TURBT, radiation, neoadjuvant/adjuvant chemotherapy,
and/or radical cystectomy with urinary diversion. Treatment
for upper tract urothelial carcinoma includes nephrectomy,
nephroureterectomy, segmental ureterectomy, and endoscopic resection of the tumor.
43 Obstructive Uropathy
Neurogenic Bladder
Most patients with urinary retention secondary to a neurogenic bladder are managed with a combination of cholinergic
medications such as bethanecol and intermittent catheterization. Patients that are unable to self-catheterize may require
indwelling catheters, although this poses an increased risk of
UTIs. In refractory cases, surgical sphincterotomy can be performed; however, this may cause urinary incontinence.
Interventional Therapy
Percutaneous nephrostomy (PCN) is a minimally invasive
procedure which utilizes imaging guidance (US, uoroscopy, CT) to place a needle and subsequent catheter into the
urinary collecting system allowing for urinary drainage and
easy access for additional procedures. The rst description
of PCN was in 1955 by Drs. Goodwin, Casey, and Wolfe
using exclusively uoroscopy and radiographic landmarks
for guidance as a “natural outgrowth” from antegrade
pyelography with an original success rate of 69%. These pioneers described difculties accessing a minimally dilated
collecting system, verifying proper positioning within the
renal pelvis, and having a sufciently long needle [27].
These issues are still worth consideration today when planning the procedural approach.
Indications for PCN recognized by the Society of
Interventional Radiology (SIR) include urinary drainage in
the presence of obstruction, urinary diversion to facilitate
healing of stula/urinary leak/hemorrhagic cystitis, access
for subsequent procedures (primarily PCNL), or need for
collecting system access when retrograde access can’t be
achieved [28].
Improvements in the technique have led to successful PCN rates ranging from 96% to 99% in multiple
studies with the SIR expected success rate of 96% in a
481
Key Point
Indications for PCN:
• Urinary drainage for obstruction
• Urinary diversion to facilitate healing
• Access for subsequent procedures
• When retrograde access can’t be achieved
simple native kidney with a dilated collecting system.
The lowest success rates of 85% are observed when
attempting PCN on non- dilated kidneys with large stag-
horn calculi [28, 29]. While this procedure can be performed on an outpatient basis, the patient’s clinical
situation may preclude this and require inpatient monitoring overnight.
Pre-procedural evaluation should include reviewing the
available imaging for kidney orientation, presence, and size
of stones, examination of the collecting system for evidence
of duplication, and presence of renal cysts or masses. The
presence of any of these abnormalities may make the
procedure technically more difcult and increase the chances
of complications. A review of the lab data is critical as the
presence of an uncorrectable severe coagulopathy is a relative or potentially absolute contraindication to the procedure.
PCN is a Category 3 procedure (signicant risk of bleeding/
bleeding difcult to detect) under the SIR guidelines; therefore, the following is recommended: platelets >50,000/mm
3
INR≤1.5, and aPTT ≤1.5× control values. A review of the
patient’s medications for any anticoagulants is also important. As a Category 3 procedure, many anticoagulants should
also be held prior to the procedure based on SIR guidelines
(Table43.5). Furthermore, it is prudent to have a discussion
with the patient and/or patient’s family regarding aftercare of
their nephrostomy tube including dressing changes, recording outputs, ushing if needed, and required follow-up care.
,
Table 43.5 SIR recommended medication hold times prior to percutaneous nephrostomy
Warfarin (Coumadin)
Heparin
Therapeutic LWMH (Lovenox) 24h/2 doses
Fondaparinux
Clopidogrel (Plavix)
Prasugrel (Efent)
Ticlopidine (Ticlid) 7days
Short-acting NSAIDS (ibuprofen, etc.) 24h
Intermediate-acting NSAIDS (naproxen, etc.) 2–3days
Long-acting NSAIDS (meloxicam, etc.) 10days
Glycoprotein 2b/3a short acting (integralin/aggrastat) 4h
Glycoprotein 2b/3a long acting (ReoPro)
Argatroban (Acova) Defer until off treatment, emergent hold for 4h
Bivalirudin (Angiomax)
Dabigatran (Pradaxa)
5days, INR≤1.5
2–4h, aPTT ≤1.5×
2–3days (CrCl >50), 3–5days (CrCl ≤50)
5days
24h, aPTT ≤1.5×, ACT <150
Defer until off treatment, emergent hold 2–3h (CrCl >50), 3–5h (CrCl ≤50)
Defer until off treatment, emergent hold 2–3days (CrCl >50), 3–5days (CrCl ≤50)
482
segmental arteries
L. A. Byers and P. J. Rochon
Apical
Anterior superior
segmental artery
Anterior inferior
segmental artery
Inferior segmental
artery
Posterior
Anterior division
Posterior division
Fig. 43.2 Lateral oblique view of the kidney viewed into the renal
hilum. The renal artery divides into anterior (ventral) and posterior
(dorsal) divisions, with the anterior division supplying the anterior twothirds of the kidney and the posterior division supplying the posterior
one-third of the kidney. The anterior division further divides into segmental arteries (apical, anterior superior, anterior inferior, and inferior
segmental arteries). The posterior division becomes the posterior
The How To
1. The patient may be positioned in either the prone
or lateral decubitus position. Often prior to sterile
preparation and draping the patient, a scout image
will be taken with marking of the anticipated entry
point. Attempting to access just posterior to the
mid-coronal plane of the kidney can potentially
reduce bleeding due to relatively decreased vascularity; this plane is called the avascular plane of
43.2).
2. If The nephrostomy tube is being placed for subsequent PCNL access, the targeted calyx should allow
segmental artery. Along the lateral and posterior aspects of the kidney,
the two renal artery divisions form an arcade of small vessels that have
sagittal plane of relatively decreased vessel density known as the avascular plane of Brodel or Brodel’s line. In addition, there are fewer vessels along the inferior aspect of this plane, and as such the inferior renal
calyx is often used as a target when placing a percutaneous nephrostomy tube, as illustrated by the needle
for the optimal surgical approach, and planning
may need to be discussed with the patient’s urologist. This may necessitate upper pole access, which
is technically more challenging and may require an
intercostal approach.
3.
and deep anesthesia, a long coaxial needle is used
to enter the collecting system under US or CT
43.3, 43.4, 43.5, and 43.6).
4. The inner stylet of the needle is removed and urine
location within the collecting system and subse-
43 Obstructive Uropathy
483
Fig. 43.3 (a) A 56-year-old male with multiple bilateral renal calculi.
Maximum intensity projection (MIP) demonstrating severe bilateral
hydronephrosis. Note that on the left, there is contrast lling the dilated
calyces and renal pelvis (thick arrow). There is also mild parenchymal
thinning (thin arrow). (b) There is severe hydronephrosis on the left
(thick arrow) with marked renal pelvis dilation, blunted calyces, and
parenchymal thinning. The hydronephrosis is due to an obstructive distal
left ureteral stone (thin arrow). (c) Longitudinal ultrasound of the same
patient, which again demonstrates severe hydronephrosis. (d) Doppler
ultrasound demonstrating signal within the renal hilum, which exhibits
“twinkle” and “comet tail” artifacts indicative of renal calculi. (e) Intraprocedural grayscale ultrasound of the kidney demonstrates needle
(thick arrows) access of the renal calyx (thin arrow). The needle will
appear as a linear hyperechoic structure. (f) Fluoroscopic image of the
same patient demonstrating placement of percutaneous nephrostomy
catheter within the left renal pelvis with iodinated contrast partially outlining the collecting system. There are multiple lling defects in the
renal calyces and renal pelvis (big arrow) that represent calculi. In addition, there is contrast pooling at a lling defect in the distal left ureter
(small arrow) corresponding to the obstructing calculi seen on CT
484
L. A. Byers and P. J. Rochon
20°-30°
Fig. 43.4 Sagittal view of the patient depicting positioning and
targeting for an inferior calyx approach ultrasound-guided nephrostomy tube. The probe should be held parallel to the long axis (sagittal
quently aspirated. Decompression followed by
setting of infection as the increase in renal pelvic
pressure can result in urosepsis.
5. A wire is advanced through the needle into the
is removed.
(a) If access of the lower urinary tract is desired,
a catheter may be used to guide the wire into
the ureters and subsequently the bladder.
(b) For nephroureterostomy tubes, the wire should
be advanced into the bladder which may require
the use of different catheters if crossing an
obstruction.
6. A nephrostomy or nephroureterostomy tube is
advanced over the wire. Once in position, the wire
can be removed.
7. The string of the catheter should be pulled back
axis) of the kidney with the needle angled at approximately 20–30°
perpendicular relative to the patient’s skin
8. If a nephroureterostomy tube is used, there should
be a pigtail coil in the bladder and in the renal
pelvis.
9. The catheter is then attached to a bag for drainage.
devices. It is important to ensure that urine still
are in place.
10. Urinary drainage should be monitored closely after
tinged, however should clear over this period. If
drainage remains bloody, evaluation of renovascular
eurysm may be performed with Doppler ultrasound,
contrast-enhanced CT, CT angiography, or conventional angiography. Note that conventional angiography remains the gold standard for evaluation of a
contrast.
allow for endovascular treatment. Hemodynamics
and lab data should also be correlated.
43 Obstructive Uropathy
Fig. 43.5 (a) Percutaneous
needle access of the right
kidney with wire coiling
within the renal pelvis. This is
further conrmed with return
of urine. (b) The percutaneous
nephrostomy tube can then be
advanced over the wire and
contrast injected into the renal
pelvis (antegrade
nephrostogram) to further
evaluate collecting system
anatomy and evaluate for
distal obstruction
485
Fig. 43.6 Common devices used for percutaneous nephrostomy tube
placement. Top to bottom: 21G Chiba needle with inner stylet, coaxial
sheath with dilator, guidewire, and pigtail nephrostomy catheter with
metallic stiffener
Key Point
The safest place to access the kidney is in the avascular
plane of Brodel, just posterior to the lateral border of
the kidney, and has a relative paucity of vessels.
Key Point
Remember, posteriorly the lung ends at the 10th rib
and the pleura ends at the 12th rib.
Key Point
A nephrostomy tube has a “pigtail” end. It can be
straightened with a plastic or metal inner stiffener,
depending on user preference. Once the tip of the catheter is into the collecting system, hold the stiffener still
and advance the remainder of the catheter over the
wire into the renal pelvis to form the pigtail. Pulling on
the string will tighten the pigtail.
After the procedure, signs and symptoms to monitor
include worsening pain at a location other than the skin incision, increasing blood in the draining urine, precipitous
decrease in nephrostomy tube output, declining hematocrit,
and new/worsening fevers or leukocytosis. Any of these
should prompt further evaluation as they are concerning for
major complications (Table43.6) [28, 30, 31].
Dressing change schedules should be tailored to ensure the
dressings remain clean and dry to prevent skin maceration and
infection. During immediate postprocedural period, the patient
or a caretaker may need to irrigate the nephrostomy tube until
the draining urine is clear to prevent clot and obstruction
within the catheter. When possible, this should be done using
clean (or even sterile) technique and sterile saline ush
syringes. Prior to disconnecting the drainage bag, ensure that
the tubing is clamped to prevent urine spillage. Clean the hub
with either chlorhexidine or alcohol and then attach the saline
ush. Irrigate the tubing with 5–10cc of saline accounting
for the length of the tubing. Clean the nephrostomy tube hub
486
L. A. Byers and P. J. Rochon
Table 43.6 Complications of percutaneous nephrostomy
Major
Septic shock 1–10%
Hemorrhage requiring transfusion 1–4%
Vascular injury requiring intervention 0.1–1%
Bowel transgression 0.2–0.5%
Pleural complications 0.1–0.6%, 8.7–12% when
Transfer to ICU, emergent surgery,
delayed discharge
Minor
Catheter dislodge/malposition 4.8%
Pelvic perforation 4.3%
Paralytic ileus 2.4%
Fever >6h 13.6
upper pole access required
1–7%
and drainage bag connector and reconnect the tubing. Ensure
that urine is once again freely owing into the drainage bag.
Nephrostomy tubes will need to be exchanged periodically
due to urine crystalline precipitation and subsequent obstruction. Classically, this was approximately every 3months; however, new research suggests that there is higher patient
compliance, reduced rate of infection, and reduced cost associated with a 2-month exchange schedule [32].
External nephrostomy tubes may ultimately be removed
once the obstruction has resolved or an internal drainage
pathway has been established such as with an internal double- J nephroureteral stent. This may be further demonstrated
with repeated antegrade nephrostogram to ensure urine ows
freely to the bladder. Despite slightly different construction
between manufactures, the steps to removing a nephrostomy
tube are essentially the same.
1. Remove all dressings and clean the skin. Ensure the
nephrostomy tube is clamped and the drainage bag is
disconnected.
2. Cut any anchoring sutures and remove any afxing devices.
Afxing devices usually have solvents to loosen the glue.
3. Grasp or use a hemostat to lightly clamp onto the tubing
near the skin and cut the catheter tubing at the hub. This
releases the string running the length of the catheter which
forms the pigtail. Have gauze ready with the other hand as
some urine will likely leak out when the tube is removed.
4. Remove the catheter. There may be some slight resis-
tance as the pigtail fully straightens; a wire can be used
to assist with this. If signicant resistance is met, stop
and reassess.
(a) For a routine exchange of the nephrostomy tube, the
catheter should be removed over a wire with plenty of
purchase of wire within the collecting system. A new
catheter is placed over the wire under uoro guidance
similar to original placement.
5. Clean the area again and apply a dry dressing.
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Enteric Access andFeeding Tubes
JiHoonShin
Pathophysiology
Enteral and parenteral feeding is commonly used in both the
inpatient and outpatient setting to provide nutritional support
and meet the metabolic requirements for patients with inadequate oral intake. Patients can tolerate up to 10days of partial fasting with IV hydration before severe protein catabolism
occurs. Feeding tubes are used for patients in whom oral
intake is either impossible or unsafe and for those unable to
maintain caloric intake orally. Furthermore, a feeding tube
can be used to decompress the bowel for those with small
bowel or gastric outlet obstruction.
44
ated by the patient for extended durations. For long-term
enteral nutrition, direct gastrostomy or gastrojejunostomy
tubes are the most reliable and best method available.
Compared with NG tube, gastrostomy demonstrated a higher
percentage of prescribed feeding and greater improvement in
nutritional state [1]. Gastrostomy tubes can be inserted surgically, endoscopically, or radiologically to suite a patients
need for enteric access.
Clinical Indications
Percutaneous Radiologic Gastrostomy
(PRG)Tube
Key Point
Enteral=feeding through the GI tract
Parenteral=delivering nutrition into a vein
The nasogastric (NG) tube and nasojejunal (NJ) tube are
rst line for patients requiring enteric access. For placement,
the tube is lubricated on the end, typically with viscous lidocaine, and inserted through a nostril. It is important for the
patients’ head to be tipped down during placement to close
the airway so that the tube does not inadvertently pass into the
trachea. Placement location is conrmed with a radiograph.
For NJ tubes, placement is ideally past the ligament of Treitz.
Direct enteral feeding by the NG or NJ route is simple;
however these tubes are prone to clog and require frequent
replacement. They are also uncomfortable and poorly toler-
J. H. Shin (*)
University of Ulsan College of Medicine, Asan Medical Center,
Department of Radiology, Seoul, Republic of Korea
e-mail: jhshin@amc.seoul.kr
Broadly, there are two main indications for feeding tube
placement, (1) enteric feeding and (2) gut decompression.
Most commonly, long-term nutritional support is needed for
patients with dysphagia. This may be secondary to numerous
etiologies including esophageal obstruction, head and neck
cancer, lesions extending into the mediastinum, and neurologic disorders. Radiologic placement is particularly useful
for patients with upper GI cancer because its placement
avoids the oral route which could disseminate tumor cells
into the stoma. Gastric decompression may be needed for
patients with gastric outlet obstruction, proximal small
bowel obstructions, or gastroparesis.
Key Point
Indications for gastrostomy tube:
• Enteric feeding
• Gastric decompression
In the pediatric population, gastrostomy tubes are fre-
quently placed in patients with hydrocephalus, severe
© Springer International Publishing AG, part of Springer Nature 2018
N. A. Keefe et al. (eds.), IR Playbook, https://doi.org/10.1007/978-3-319-71300-7_44
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