THE URINARY TRACT
Methods of examination
Plain film of the abdomen – patient in supine position, kidneys,
ureteral and bladder areas. Assessment of the size, shape and position of
the kidneys, the presence of calcium, psoas muscle abnormalities.
IVU – i.v. injection of radioopaque contrast medium. Serial films are
obtained over 25 minutes as the contrast agent is excreted by the kidneys
for visualization of the renal collecting system, ureters and bladder (first
film obtained after 1 minute and a second film after 5 minutes).
Compression – film. Patient preparation – bowel cleansing to remove gas
and fecal matter from the colon.
Contraindications to injection of i.v. contrast medium :
- hypersensitivity to the contrast agent
- renal and hepatic disease
- asthma
- a serum creatinine level higher than 1,5 – 1,8 mg/100ml
- multiple myeloma
- history of severe allergy
US
CT
MRI
Retrograde pyelography – cystoscopy and catheterization of the
ureters are necessary.
Antegrade pyelography – a needle is placed percutaneously into the
renal pelvis from a posterolateral approach and either fluoroscopic or
ultrasonic guidance is used.
Conventional percutaneous nephrostomy, brush biopsy, stent
placement, stone dissolution or extraction, dilation of stenosis can be
performed
Renal angiography – first global aortography followed by selective
renal artery catheterization. Used for renal angioplasty/stenting and renal
embolization.
Cystography – a urethral catheter is inserted and the bladder is filled
with contrast medium. Indications: bladder rupture, tumors, diverticula.
Renal scintigraphy – 99Tc. Indication – renal function.
Anomalies in number
Renal agenesis – single kidney.
Method of choice – angiography.
Supernumerary kidney
–the anomalous kidney is small
- the other kidney on the same side is often smaller
than the normal kidney on the opposite side.
- demonstration of the presence of a separate pelvis,
ureter and blood supply is necessary for the diagnosis.
Anomalies in size and form
Hypoplasia
– usually associated with hyperplasia on the other side.
- The hypoplastic kidney functions normally.
- the collecting system is small
- there is a normal relation between the amount of
parenchyma and the size of calices and renal pelvis.
- Differentiai diagnosis - acquired atrophic kidney – small
kidney because of vascular or inflammatory disease.
Anomalies in size and form
-
Hyperplasia – is associated with agenesis or hypoplasia
on the opposite side
- more properly termed compensatory hypertrophy.
Conditions that usually cause bilateral renal enlargement:
acute glomerulonephritis,
lymphoma, leukemia in children,
systemic lupus erithematosus,
polycystic disease,
bilateral renal vein thrombosis,
amyloidosis,
sarcoidosis,
lobular glomerulonephritis,
total lipodystrophy.
Fusion anomalies
Horseshoe kidney – the lower poles of the kidney are
joined by a band of soft tissue, the isthmus.
- the long axis of the kidney is reversed  the lower pole is
nearer the midline than the upper.
- associated rotation anomaly  the calyces are directed
backward or posteromedially.
- the ureters tend to be streched over the isthmus  partial
obstruction is not unusual  dilation of the pelvis and
calyces.
Crossed ectopy – fusion of the kidneys on the same side;
- the lower kidney is ectopic and its ureter crosses the
midline to enter the bladder normally on the opposite side.
Anomalies in position
Ectopy – pelvis, thorax
Nephroptosis – downward displacement and more
mobility of the kidney than usual.
Malrotation – results from incomplete or excessive
rotation and urographic study indicates the degree of
anomaly.
PA
Anomalies of the renal pelvis and ureter
Ureteropelvic junction anomalies
– bilateral but not always simmetrical.
Duplication of the pelvis and ureter
Retrocaval ureter – is limited to the right side.
- The ureter passes to the left behind the IVC.
Ureterocele – intravesical dilation of the ureter immediately
proximal to its orifice in the bladder.
- resembles a cobra head in shape.
- When the ureterocele is not filled with contrast radiolucent mass within the opacified bladder in the region of
the ureteral orifice.
- If it is filled, the lesion is outlined by a radiolucent
wall that stands out in contrast to the filled bladder and to the
filled, dilated, distal ureter.
Ureteral diverticula
OBSTRUCTIVE UROPATHY
Nonobstructive hydronephrosis
– diabetes,
- infections,
- appendicitis, peritonitis
Congenital hydronephrosis
– obstruction at the UPJ,
- vesicoureteral reflux,
- congenital ureterocele,
- urethral valves, congenital strictures.
Acquired hydronephrosis
– tumors,
- calculi,
- strictures,
- radiation therapy,
- surgery,
- prostatic enlargement,
- pregnancy in the third trimester.
OBSTRUCTIVE UROPATHY
Imaging findings
-US method of first choice to evaluate patients with suspected
hydronephrosis (mild, moderate, severe).
-CT + i.v.contrast medium – useful to assess the cause of obstruction.
-Urography
– early : flattening of the normal concavity of the calyx + decrease in the
rate of contrast material accumulating in the collecting system.
- Calyces then gradually enlarge with progressive destruction of
parenchyma.
- A prolonged and increasingly dense nephrogram is characteristic of
acute renal obstruction.
- In severe cases do percutaneous nephrostomy.
T
CALCULI
Incidence – 5% of population; 20% at autopsy.
Recurrence of stone disease – 50%.
Predisposing conditions – calyceal diverticuli, renal tubular
acidosis, hypercalcemia, hypercalciuria.
The radiographic density of a calculus depends on its calcium
contents:
- Calcium calculi (opaque) 75% - calcium oxalate and
phosphate.
- Struvite calculi (opaque) 15% - magnesium ammonium
phosphate:”infection stones”;
- Cystine calculi (less opaque) – cystinuria.
- Nonopaque calculi – uric acid, xanthine, mucoprotein matrix
calculi in poorly functioning, infected urinary tract.
Radiographic features
Calculus - determine size, number, location
Radioopaque calculus are best detected on KUB or helical CT
Radiolucent calculi are best detected by IVU
US – renal calculi - hyperechoic focus, posterior shadowing
IVU
- Delayed and persistent nephrogram  ureteral obstruction
- Ureter distal to calculus is narrowed (edema, inflammation),
may create false impression of stricture
- Ureter proximal to calculus is persistently minimally dilated
CT
- detects most calculi regardless of calcium content
- Helical CT is very useful to detect small calculi
Location – 3 narrow sites:
UPJ, at crossing of ureter with iliac vessels, UVJ
Complications:
- Forniceal rupture (pyelosinus backflow)
- Chronic calculous pyelonephritis
- XGP
Treatment options:
-Small renal calculi ( 2,5cm) – ESWL
(extracorporeal shock wave lithotripsy)
- Large renal calculi ( 2,5 cm) – percutaneous removal
- Upper ureteral calculi – ESWL
- Lower ureteral calculi – ureteroscopy
Differential diagnosis
- Gallstones
- Calcification of costal cartilage
- Calcified mesenteric nodes
- Calcifications in cysts and tumors
- Vascular calcification
Staghorn calculus
URINARY TRACT INFECTION
Acute pyelonephritis
Acute bacterial infection of the kidney and urinary tract – Proteus,
Klebsiella, E.Coli
Types - focal type – lobar nephronia
- diffuse type – more severe and extensive
Role of imaging studies:
- Define underlying pathology – obstruction, reflux, calculus
- Rule out complications – abscess, emphisematous pyelonephritis
Radiographic features
US - renal enlargement (edema)
- loss of corticomedullary differentiation (edema)
- IVU – delay of contrast excretion, narrowing of collecting system,
striated nephrogram,
- CT - areas of decreased perfusion by
Chronic pyelonephritis
Criteria for diagnosis:
- Scarring - can affect the entire thickness of renal substance
 the involved papilla is retracted  secondary dilation of its
calyx
- the involved area irregular surface depression
- The dilated calyx - smooth margin, variable shape
- Renal tissue adjacent to the involved area is normal or
hypertrophied
- unifocal or multifocal, one or both kidneys
- decreased size of the involved kidney
RENAL ABSCESS
Usually caused by gram negative bacteria.
Underlying disease – calculi, obstruction, diabetes, AIDS.
Radiographic features
Well-delineated focal renal lesion
Central necrosis
Thickened abscess wall with contrast enhancement
Perinephric inflammatory involvement
Complications: retroperitoneal spread of abscess,
renocolic fistula
TUBERCULOSIS
GU tract is the second most common site of TB involvement after the
lung. The disease is typically due to hematogeneous spread.
Clinical – history of pulmonary TB, pyuria, hematuria, dysuria
Radiographic features
Distribution – unilateral involvement is more common – 70%
Size – early - kidneys are enlarged
- late - the kidneys are small, autonephrectomy
Parenchyma - calcifications – curvilinear, mottled, amorphous
- Papillary necrosis, parenchymal cavity
- Tuberculoma
- Parenchymal scarring
Collecting system
- infundibular stenosis
- amputated calyx
- Corkscrew ureter – multiple stenosis
- “pipestem” ureter - narrow, rigid, aperistaltic segment
CYSTIC DISEASE
Symple cysts
Probably arise from obstructed tubules or ducts.
They do not communicate with the collecting system.
Clinical – most commonly asymptomatic; rare hematuria
Radiographic features
IVU – lucent defect, cortical bulge, round indentation on the
collecting system
US – anechoic, sharply marginated, smooth walls, very thin
septation may be seen
CT – homogeneous water density, no enhancement.
- smooth cyst wall, sharp demarcation from the
surrounding renal parenchyma
Complicated cysts – Bosniak classification:
- category 1 lesions – benign simple cyst
- category 2 lesions – these minimally complicated cysts are
benign but have certain radiologic findings of concern.This
category includes septated cysts, minimally calcified cysts,
high-density cysts
- category 3 lesions – complicated cystic lesions that exibit
some radiologic patterns also seen in malignancy. This
category includes complex septated cyst, heavily calcified
cyst. Surgery is usually performed
- category 4 lesions – clearly malignant lesions with large
cystic component. Irregular margins, solid vascular elements
ADULT POLYCYSTIC KIDNEY DISEASE
Cystic dilation of collecting tubules as well as nephrons.
Autosomal dominant trait.
Clinical – slowly progressive renal failure.
Treatment – dialysis, transplant.
Associated findings – hepatic cysts, intracranial aneurysm,
cysts in pancreas and spleen.
Radiographic features
-kidneys are enlarged and contain innumerable cysts, creating
a boselated surface.
-They do not communicate with the collecting system
- calcification of cyst wall is common
- pressure deformities of calyces and infundibula
- “swiss-cheese” nephrogram
BENIGN TUMORS
Angiomyolipoma
Hamartomas containing fat, smooth muscle and blood vessels.
Treatment – small lesions are not treated; large and symptomatic lesions
are resected or embolized
Complication – tumors may spontaneously bleed because of their
vascular elements
CT method of choice
Adenoma
Low grade adenocarcinoma with no metastatic potential.
Usually detected at autopsy
Oncocitoma
These tumors arise from oncocytes of the proximal tubule.
Radiographic features – central stellate scar (CT) , well-defined sharp
borders
Juxtaglomerular tumor (reninoma)
Secretion of renin causes HTN, hypernatremia, hypokalemia.
Tumors appear as small hypovascular masses
RENAL CELL CARCINOMA
Synonyms – renal adenocarcinoma, hypernephroma, clear cell
carcinoma
Clinical – hematuria, flank pain, palpable mass, weight loss,
paraneoplastic syndrome: hypertension (renin), erythrocytosis
(erythropoietin), hypercalcemia (PTH), gynecomastia
(gonadotropin), Cushing syndrome (ACTH)
Risk factors – tobacco, phenacetin long term use, Von HippelLindau disease, chronic dialysis, family history
Radiographic features
IVU – renal mass with renal contour deformity,
- calyceal displacement and destruction
US – hypoechoic, nonhomogeneous, irregular borders
CT – hypodense mass, enhancement
- calcifications, necrosis, irregular borders
Angiography
– hypervascular, caliber irregularities of tumor vessels,
- prominent AV shunting, venous lakes,
- preoperative embolization
Staging
Stage I – tumor confined to kidney
Stage II – extrarenal but confined to Gerota’s fascia
Stage III A – venous invasion; B- lymph node metastases ; C – both
Stage IV A – direct extension into adjacent organs ;
IV B – metastases (lung, liver, bone, adrenal, contralateral kidney)
Therapy – radical nephrectomy, chemotherapy, radiotherapy
Renal pelvis tumors – transitional cell carcinoma
Tumors are often multifocal – ureter, bladder.
Radiographic features –
- irregular filling defect - polypoid mass.
- wall thickening – infiltrative cancer
Staging
Stage I – mucosal lamina propria involved
Stage II – into but not beyond muscular layer
Stage III – invasion of adjacent fat / renal parenchyma
Stage IV - metastases
URINARY BLADDER
D
T