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Urinary System

Urinary System Anatomy

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Kidneys lie 30° from the midcoronal plane

Best visualized when the affected side is

obliqued up (places kidney parallel to IR)

LPO best visualizes= right kidney

RPO best visualizes = left kidney

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Physiology of the

Urinary System

Kidney

Nephron

○ Functional unit of the kidney

○ Over 1 million in each kidney

○ Functions

Filters

Reabsorbs

Excretes

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Physiology of the

Urinary System

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Physiology of the

Urinary System

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Physiology of the

Urinary System

Filters waste products from the blood

○ More than 1 L of blood filtered per minute

○ 180-190 L of filtrate removed from blood every 24 hours

Reabsorbs water & nutrients

○ 99% of water reabsorbed into blood

Secretes excess substances in the form of urine

○ 1.5 L of urine formed daily

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Physiology of the

Urinary System

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Physiology of the

Urinary System

Acid-base balance

pH of blood = 7.35-7.45

If it is too acidic – kidney excrete acidic urine to

remove hydrogen ions

If it is too alkaline – kidneys excrete alkaline urine to

preserve hydrogen ions

Peristaltic waves force urine down ureters into bladder

1-5 minutes

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Physiology of the

Urinary System

3 constricted points of the ureter

Ureteropelvic junction (UPJ) - where renal pelvis funnels down into small ureter

Pelvic brim – where iliac blood vessels cross over the ureters

Ureterovesical junction (UVJ) – where ureter joins bladder

○ Enters at posterior lateral portion of bladder

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Anatomy of the Urinary bladder

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Physiology of the

Urinary System

Urinary bladder

Acts as a reservoir for urine before it leaves body

Trigone

○ Triangle-shaped floor

○ Formed by UVJs & opening of urethra

Total capacity of adult bladder = 350-500 mL

Micturition – (voiding)

○ Desire to void stimulated by autonomic nerve endings in the

wall

○ 250 mL-usually when the urge is simulated

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Physiology of the

Urinary System

Contractions & relaxation of sphincter

muscles permits bladder to expel urine

through urethra

Voluntary contractions

○ Learned

○ Only possible when motor system is intact

Incontinence

○ Involuntary emptying of bladder

○ May be caused by nervous system injuries such as

cerebral hemorrhage, or spinal cord injury

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Physiology of the

Urinary System

Other functions of kidneys

Produces erythropoeitin

○ Stimulates rate of production of RBCs

○ Renal failure = severe anemia

Produces angiotensin

○ Formed by renin secreted by cells with renal

arterioles & plasma proteins

○ Decreased blood flow through arterioles increases

secretion of renin & angiotensin, constricts

peripheral arterioles & elevates blood pressure

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Congenital/Hereditary

Congenital / Hereditary Diseases

Anomalies of number & size

Renal agenesis-Solitary kidney

○ Must exclude nonfunctioning, diseased kidney or

prior nephrectomy

○ Results from failure of the embryonic renal vascular

system to form

○ Ureter & corresponding half of trigone usually

missing

○ Tends to be larger–“Compensatory hypertrophy”

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Renal agenesis-Solitary

Kidney

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Intr

aven

ous

Pyel

ogra

m

Renal agenesis

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Supernumerary kidney- 3 kidneys

3rd usually small

Possesses separate pelvis, ureter, & blood

supply

Functions normally

May lead to secondary infections that may

eventually require removal

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Hypoplastic kidney

Miniature replica of normal kidney

Proportional

○ Good function & normal relationship between the

amount of parenchyma & size of collecting

system

Not the same as an acquired atrophic kidney

○ Small & contracted because of vascular or

inflammatory disease

○ reduces the volume of renal parenchyma

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Compensatory hypertrophy

Acquired condition that develops when one

kidney is forced to perform the function

normally carried out by 2 kidneys

May follow renal agenesis, hypoplasia,

atrophy, or nephrectomy

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Compensatory hypertrophy

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Anomalies of rotation, position, & fusion

Malrotation

○ May produce bizarre appearance that may suggest

pathologic condition, but is otherwise normal

○ Renal pelvis turned from medial position into

anterior or posterior position

○ UPJ may be seen lateral to kidney

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Malrotation

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Ectopic kidney

Abnormally positioned kidney

○ Pelvic kidney ( in the pelvis)

Often in right pelvis

○ Intrathoracic kidney ( above the diaphragm)

Usually functions normally,

Visualization may be obscured due to overlying

bone & fecal contents

Crossed ectopic

○ Ectopic kidney lies on same side as normal kidney

& very commonly fused with it

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Crossed ectopic

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Intrathoracic kidney

( above the diaphragm)

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Fusion-Horseshoe kidney

○ Most common type of fusion anomaly

○ Both kidneys malrotated

○ Lower poles joined by normal renal

parenchyma (isthmus) or connective tissue

○ Ureters arise from kidneys anteriorly instead

of medially

Possible site of obstruction at UPJ

○ Lower poles point medially rather than

laterally

○ Pelvis large & “flappy” simulating obstruction

More prone to infection

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Horseshoe kidney

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Horseshoe kidney

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CT

SC

AN


○ Complete fusion

Single irregular mass that has no resemblance to a

renal structure

Bizarre appearance

“Disk, cake, lump, & doughnut kidney”

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Anomalies of renal pelvis & ureter

Duplication (duplex kidney) ○ Common anomaly that may vary from simple bifid

pelvis to a completely double pelvis, ureter, & UVJ

○ Ureter draining upper renal segment enters bladder below ureter draining the lower renal segment

Complete duplication ○ Obstruction More frequently affects upper pole

○ Vesicoureteral reflux with infection Reflux most commonly involves ureter draining lower

segment

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Treatment of anomalies Most case no treatment required

Infection

○ Antibiotics

○ Determine anatomic cause that can be corrected surgically

Obstruction - therapy

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Ureterocele

Cystic dilatation of the distal ureter near its

insertion into the bladder

Simple (adult) type

○ Opening in ureter situated at or near the

normal position

○ Stenosis of ureteral orifice with varying

degrees of dilatation of the proximal ureter

Leads to prolapse of the distal ureter into the

bladder & dilatation of the lumen of the prolapsed

segment

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Ectopic ureteroceles

Seen almost exclusively in infants & children

Associated with ureteral duplication

Radiographic appearance - simple

Filled with contrast

○ “Cobra head sign”

Not filled with contrast

○ Appears as a radiolucent mass within the opacified

bladder

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Treatment

○ May need to be treated to preserve kidney

function & to reduce risk of infection

○ Endoscopic incision of ureterocele at UVJ

Allows normal urine drainage into the bladder

○ Surgical resection & bladder reconstruction

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Ectopic ureterocele-Cobra Head

sign

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Ectopic ureterocele

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Ectopic ureterocele

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Ectopic ureterocele with

Hydronephrosis

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Posterior urethral valves

Thin transverse membranes, found almost

exclusively in males, that cause bladder outlet

obstruction

May lead to severe hydronephrosis, hydroureter,

& renal damage

Work as a reverse valve

○ Catheterization is normal but the valve prevents

antegrade flow

○ Best demonstrated on VCUG

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Treatment

Surgery

○ Correct anatomic relationships

○ Allow normal urine flow to prevent kidney or

ureteral obstruction

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Posterior urethral valves

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Urinary System

Pathology

Inflammatory Disorders

Inflammatory

Disorders

Pyelonephritis

Suppurative inflammation of the kidney & renal pelvis

caused by pyogenic bacteria

Affects interstitial tissue between tubules

Often only one kidney involved, asymmetric if both

involved

Infection usually originates in bladder & ascends by

means of ureter to involve kidneys

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Inflammatory Disorders-

Pyelonephritis

Radiographic appearance - acute

Most IVPs – normal

Abnormalities

○ Enlargement of kidney on symptomatic

side

○ Delayed calyceal opacification

○ Decreased density of contrast material

○ Linear striation in renal pelvis – mucosal

edema

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Inflammatory Disorders-

Pyelonephritis

Radiographic appearance - chronic

Hallmark sign

○ Patchy calyceal blunting/clubbing with overlying

parenchymal scarring

May lead to end-stage renal disease with small,

irregular, poorly functioning kidneys

Treatment

Antibiotic therapy

Surgery or percutaneous drain placement

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Pyelonephritis

Hallmark sign – “clubbing”

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Inflammatory Disorders

Emphysematous pyelonephritis

Severe form of acute parenchymal

Perirenal infection with gas-forming bacteria

Occurs virtually only in diabetic patients

Causes necrosis of the entire kidney

Radiographic appearance

○ Radiolucent gas shadows within & around the kidney

Treatment

○ Surgical emergency

○ Lethal if treated medically

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Emphysematous pyelonephritis

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Tuberculosis

Spread by hematogenous route

Small granulomas scattered in the kidney

cortex

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Tuberculosis

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•Secondary infection


•Spread to renal pyramid

•Ulcerative, destructive process

in tips of papillae

•Irregularity & enlargement of the

calyces

• Fibrosis & stricture formation

Tuberculosis

Progression

Irregular calcifications

Entire nonfunctioning

renal parenchyma may

be replaced by massive

calcification

(autonephrectomy)

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Tuberculosis

Ureter & bladder involvement Multiple ulcerations

“Beaded or corkscrew appearance” – after healing

Treatment 6-8 months of a combination of

powerful tuberculostatic drugs

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Cystitis

Inflammation of the urinary bladder

Most common in women

Causes

Spread of bacteria present in fecal material

Instrumentation or catheterization of the bladder

○ Most common nosocomial infection

Sexual intercourse

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Cystitis

Symptoms

Urinary frequency

Urgency

Burning sensation during urination


Acute

○ Generally no detectable changes on IVP

Chronic

○ Decrease in bladder size associated

○ Irregularity of the bladder wall (filling defects) Due to fungus, blood clots

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Cystitis

Emphysematous cystitis

○ Occurs most often in diabetic patients

○ Caused by gas-forming bacteria

○ Plain film

Ring of lucent gas outlining all or part of the bladder

wall OR:

Presence of gas within bladder lumen

Treatment

Antibiotic & sulfa drug therapy

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Emphysematous cystitis

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Kidney Stones

Asymptomatic until they lodge in the ureter &

cause partial obstruction

Varying causes

Underlying metabolic abnormality

○ Hypercalcemia – increased calcium excretion in the

urine

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Kidney Stones

Small stones (3 mm or less) may pass spontaneously

Staghorn calculus

Stone may completely fill renal pelvis

Nephrocalcinosis

Calcium deposits within renal parenchyma

Caused by hyperparathyroidism or increased intestinal absorption of calcium

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Staghorn calculus

Kidney Stones

Ureteral calculi

Small, irregular, poorly calcified, easily missed on plain films

Common at pelvic brim & UVJ

Bladder calculi

Disorder primarily of elderly men with obstruction or infection of lower urinary tract

Associated with bladder-outlet obstruction, urethral strictures, bladder diverticula

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Kidney Stones


Plain abdominal films

○ 80% of renal stones contain enough calcium to

be radiopaque & detectable

○ 34% of stones are missed due to their size,

location, or because of overlying bowel or bone

Noncontrast helical CT

○ Used most frequently to best demonstrate

stone without anatomically obscuring the area

○ Safer, easier, & 95% more accurate than IVP

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Kidney Stones

Ultrasound

Used when ionizing radiation is contraindicated

Cannot detect stones smaller than 3 mm

IVP

Stones appear as filling defects in contrast-filled

collecting system

May demonstrate point of obstruction & dilation of

proximal ureter & pelvicalyceal system

May cause delayed & prolonged nephrogram

○ Lack of calyceal filling

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Kidney Stones

Treatment

Prevention

○ Increasing fluid intake

○ Decreasing intake of stone-forming

substances

Chemolysis - Medication by percutaneous

catheter to dissolve stones into small

pieces that pass more easily.

Lithotripsy

○ Use of shock waves to break up stones

○ Works well for stones above pelvis brim

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Kidney Stones

Cystoscopic retrieval or laser

destruction

For stones in the pelvis

Surgery

Last resort

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Staghorn calculus

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Obstructed left ureter due to calculus;

dilated collecting system.

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Stone as nonopaque filling defect

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Bladder stones

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Urinary Tract Obstruction

Major causes in the adult

Urinary calculi

Pelvic tumors

Urethral strictures

Prostate gland enlargement (males)

Major causes in children

Congenital malformations

○ UPJ narrowing, ureterocele, posterior urethral

valve

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Common sites

UPJ

Pelvic brim

UVJ

Bladder neck

Urethral meatus

Blockage above level of bladder can

cause hydroureter & hydronephrosis

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CT

○ Detects mass effects, stones, or other causes

of obstruction better than IVP

Acute obstruction

○ Delayed parenchymal opacification of contrast

○ Greater concentration of the contrast material

○ Enlarged kidneys with moderately dilated

calyces

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Treatment Decompression of the urinary

tract to prevent parenchymal damage & possible ureteral rupture

Percutaneous nephrostomy (for drainage)

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Cysts & Tumors

Renal cyst

Most common unifocal masses of the

kidney

Fluid-filled, unilocular

○ May have septa that sometimes divide

cyst into chambers

Vary in size

May be single or multiple in one or both

kidneys

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Renal cyst


Thin, smooth, radiopaque rim around bulging lucent

cyst

Thickening of rim

○ Suggestive of bleeding into cyst, infection, or

malignant lesion

Displacement of adjacent portions of the pelvicalyceal

system

Ultrasound

Modality of choice for distinguishing fluid-filled cysts

from solid mass lesions

Fluid-filled = echo-free (anechoic)

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Cysts & Tumors

Polycystic Kidney Disease

Inherited disorder

Multiple cyst of varying size cause lobulated

enlargement of the kidneys

Progressive renal impairment caused by

compression of nephrons

1/3 of patients have cysts of the liver

10% - have saccular (berry) aneurysms of cerebral

arteries (often fatal)

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Cysts & Tumors

Renal cell carcinoma

(hypernephroma)

Most common renal neoplasm

Predominates in patients >40 yrs with painless hematuria

10% - involve calcification around areas of tumor necrosis

90% of all masses containing calcium in nonperipheral locations are malignant

Classic triad of symptoms (10%)

○ Hematuria, flank pain, possible palpable abdominal mass

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Localized or generalized renal enlargement

Initially – elongation of adjacent calyces

Progression – enlargement leads to

obliteration of part or all of collecting system

Large tumors may partially obstruct pelvis or

upper ureter

Treatment

Nephrectomy

○ Most common treatment

○ 40% survival rate

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Inhomogeneous mass

Cysts & Tumors

Wilms’ tumor

(nephroblastoma)

Most common abdominal neoplasm of infancy & childhood

Arises from embryonic renal tissue

Tends to become very large & appear as a palpable mass

Highly malignant

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Wilms’ tumor (nephroblastoma)


Pronounced distortion & displacement of the pelvicalyceal system

Ultrasound

Valuable in distinguishing Wilms’ tumor from hydronephrosis

Determines intrarenal location of Wilms’ tumor versus extrarenal origin of neuroblastoma

CT

○ Shows full extent of the tumor

○ Detects any recurrence of neoplasm after surgical

removal

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Wilms’ tumor (nephroblastoma)

Treatment

85% cure rate

○ Surgery

○ Radiation therapy

○ chemotherapy

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Cysts & Tumors

Carcinoma of the

bladder

Usually seen in men over the age of 50

Predisposing factors

○ Smoking

○ Exposure to industrial chemicals

○ High incidence of parasitic infection (ex:

schistosomiasis in Egypt)

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Carcinoma of the bladder


Fingerlike projections into lumen or infiltrating into

bladder wall

Plain films

○ Calcifications usually encrusted on surface or

within tumor

IVP

○ Can detect only about 60% of bladder

carcinomas

○ Small when first symptomatic

○ Located on trigone – difficult to visualize

○ Lower urinary tract hematuria – cystoscopy to

exclude bladder CA 86


CT

○ Full distention of bladder

○ Mass projecting into bladder lumen or as focal thickening of bladder wall

○ Can determine presence & degree of extravesical extension, involvement of the pelvic sidewalls, & enlargement of pelvic or paraaortic lymph nodes

Treatment

Low grade of malignancy but tend to recur repeatedly after surgical removal

For invasive tumors

○ Removal of the entire bladder with ileostomy. 87


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Benign prostatic

hypertrophy

Tumor

Acute Renal Failure

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Acute Renal Failure

Rapid deterioration in kidney function

Results in the accumulation of nitrogen-

containing wastes in the blood &

characteristic ammonia odor of the

breath

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Acute Renal Failure

Urine output decreases to less than 400 ml

per 24-hour period


Ultrasound

○ Demonstrates dilatation of ureters & pelves

○ Can assess renal size & presence lesions or cystic

disease

○ Can distinguish between low blood volume from

right-sided heart failure in prerenal failure patients

Heart failure – dilatation of IVC & hepatic veins

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Acute Renal Failure

Tomography

Acute renal parenchyma dysfunction – bilaterally

enlarged, smooth kidneys

Chronic, preexisting renal disease – small kidneys

Bilateral renal calcification

IVP

Bilateral renal enlargement with delayed & prolonged

nephrogram

Excretion of contrast by liver opacifying gallbladder

Not advised - contrast material believed to further

damage kidneys

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Acute Renal Failure

Ultrasound

Modality of choice – no contrast required

Treatment Treatment of predisposing conditions to reduce risk

Diuretics to increase urine flow

Vasodilators to increase renal blood flow

Dietary modifications to decrease load on kidneys

○ Decreasing potassium & protein intake, increase carbs

Antibiotics

Renal dialysis

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Chronic Renal Failure

Chronic kidney dysfunction – may reflect prerenal, postrenal, or intrinsic kidney disease

Underlying causes Bilateral renal artery stenosis, bilateral ureteral

obstruction, renal disorders (chronic glomerulonephritis, pyelonephritis)

Uremia Failure to clear nitrogen-containing wastes adequately

from circulation resulting in the accumulation of excessive blood levels of urea & creatinine (waste products of protein metabolism)

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Toxic effects of uremia

GI tract – nausea, vomiting, diarrhea

Nervous system – drowsiness, decreased

mental ability, coma

Circulatory system - Decreased ability to

synthesize erythropoietin – resulting in anemia

Skin – intense itching (pruritus) & yellowish

coloring resulting from the combined effects of

anemia & retention of a variety of pigmented

metabolites

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Ultrasound

○ Modality of choice

○ Assess renal size & presence of lesion or cystic disease

○ Diagnose treatable diseases such as hydronephrosis

Plain films

○ Bilateral renal calcifications – nephrocalcinosis

○ Obstructing ureteral stones

○ Kidney size

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Treatment

Slow nephron loss & minimize

complications

○ Antihypertensive drugs

Balance fluid & electrolyte levels

○ dialysis

Kidney transplant

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