Ch 6- Urinary Tract Practice Flashcards

Physiology of the Urinary System

• System Components: Consists of the kidneys, ureters, urinary bladder, and urethra.

• Coordinated Function: These organs work together to filter blood and eliminate metabolic waste products from the body.

• Primary Roles:

  • Filtering the blood.

  • Removing waste products of metabolism.

  • Regulating body fluids.

  • Excreting urine.

• Homeostasis: The main purpose is the maintenance of homeostasis by regulating water balance, electrolyte concentrations, and acid-base levels in the body.

Anatomy of the Urinary System

• Kidneys:

  • Description: Primary organs of the urinary system responsible for filtering blood and producing urine.

  • Location: Situated on either side of the spine, below the rib cage.

  • Functional Unit: The nephron is the microscopic unit of the kidney. It filters blood and forms urine via filtration, reabsorption, and secretion.

  • Key Functions:

    • Filtering waste products and drugs from the blood.

    • Removing toxic metabolic waste.

    • Regulating fluids and electrolytes, specifically sodium and potassium.

    • Maintaining acid-base balance.

    • Releasing hormones: Erythropoietin (stimulates red blood cell production).

    • Regulating blood volume and blood pressure.

• Ureters:

  • Description: Paired, narrow muscular tubes.

  • Function: Transport urine from the kidneys to the urinary bladder.

  • Mechanism: Propel urine using peristaltic (wave-like) muscle contractions.

  • Connection: They link the renal pelvis of the kidney to the bladder.

• Urinary Bladder:

  • Description: A hollow muscular organ located in the pelvic cavity used for temporary urine storage.

  • Dynamics: Walls expand to store urine and contract during the process of urination.

  • Capacity: The average adult bladder capacity is approximately $2$ cups for several hours.

• Urethra:

  • Description: A tube carrying urine from the bladder to the exterior of the body.

  • Regulation: Controlled by sphincter muscles that regulate flow.

  • Gender Differences: In males, it also serves as a passageway for semen during ejaculation.

• Internal Anatomy (Visual Labels):

  • Inferior Vena Cava and Descending Aorta.

  • Adrenal gland.

  • Renal artery and Renal vein.

  • Renal pelvis, Medulla, Renal column, Medullary pyramid, Cortex.

  • Normal Nephron Anatomy: Comprised of the Glomerulus, Distal tubule, and Proximal tubule.

Congenital and Hereditary Diseases

• Definition: Disorders present at birth or resulting from genetic mutations affecting the kidneys, ureters, bladder, or urethra.

• Clinical Manifestations:

  • Most are asymptomatic and discovered incidentally.

  • Normal kidney function is typically maintained throughout life if at least one kidney remains healthy.

• Diagnosis:

  • Prenatal and postnatal ultrasound.

  • CT or MRI for high-detail imaging.

  • Nuclear medicine renal scans for functional evaluation.

• Complications:

  • Urinary tract infections (UTIs).

  • Kidney stones.

  • Hydronephrosis.

  • Abdominal or flank pain.

  • Hypertension.

  • Proteinuria (protein in urine).

  • Reduced kidney function and Hematuria.

• Treatment and Management:

  • Typically, no treatment is required.

  • Protect the unaffected kidney; monitor kidney function and blood pressure.

  • Test urine for protein and avoid nephrotoxic medications.

• Imaging Modalities:

  • Ultrasound: The "Gold Standard" and first-line technique. Safe, noninvasive, no ionizing radiation. Detects abnormalities in size, structure, and position.

  • CT: Provides precise anatomical cross-sectional information.

  • MRI: Useful for complex anomalies without radiation.

  • Renal Scintigraphy (NM): Determines how well each kidney drains and functions.

Anomalies of Number and Size

• Unilateral Renal Agenesis (URA):

  • Congenital failure of one kidney and its associated ureter to develop.

  • The single functional kidney undergoes compensatory hypertrophy.

  • Often asymptomatic; associated with Vesicoureteral Reflux, Hydronephrosis, reproductive tract abnormalities (females), or Hypospadias (males).

• Bilateral Renal Agenesis: Incompatible with life; usually results in death in utero.

• Supernumerary Kidney:

  • A rare anomaly featuring an additional (third) kidney.

  • Equipped with its own blood supply, collecting system, and capsule.

  • Usually small, rudimentary, and located below the normal kidney on the same side.

• Hypoplastic Kidney (Renal Hypoplasia):

  • Reduction in kidney size due to an incomplete number of nephrons.

  • Unilateral: Most common; one small and one normal kidney.

  • Bilateral: Both are underdeveloped; can lead to chronic kidney disease or failure in childhood.

Anomalies of Rotation, Position, and Fusion

• Kidney Malrotation:

  • Abnormal orientation; the hilum does not face medially.

  • Variations: Failure to rotate, incomplete rotation, excessive rotation, or rotation in the wrong direction.

• Ectopic Kidney:

  • Kidney located outside the normal renal fossa.

  • Pelvic Kidney: Most common; remains in the pelvis near the bladder.

  • Abdominal Ectopic: Partial ascent above the pelvis but below the renal fossa.

  • Thoracic (Intrathoracic): Extremely rare; located in the thoracic cavity.

  • Crossed Renal Ectopia: Kidney crosses to the opposite side and may fuse with the other kidney.

• Horseshoe Kidney:

  • Most common renal fusion anomaly.

  • Kidneys fuse at the lower poles, forming a U-shape across the midline.

  • Located lower in the abdomen; fusion occurs anterior to the aorta and Inferior Vena Cava (IVC).

  • An isthmus connects the two kidneys.

• Fused Kidney (Pancake/Doughnut Kidney):

  • AKA: Pancake kidney, fused pelvic kidney, complete renal fusion, disk, lump, or doughnut kidney.

  • Complete fusion of both kidneys into a single mass without a separating septum, usually remaining in the pelvis.

Anomalies of the Renal Pelvis and Ureter

• Duplex Kidney (Duplicated Collecting System):

  • Partial Duplication (Bifid System): Two renal pelves merge into one ureter (bifid ureter) before the bladder.

  • Complete Duplication: Two separate ureters drain the kidney independently.

• Ureterocele:

  • Cystic dilation of the distal ureter at the bladder entry point caused by stenosis of the ureteral orifice.

  • Intravesical: Located entirely within the bladder; common in adults with single systems.

  • Ectopic: Extends beyond the bladder neck; common in children with duplicated systems.

  • Clinical Presentation: In infants, it causes UTIs, failure to thrive, and hydronephrosis. In adults, it causes stones and flank pain.

  • Diagnosis: Ultrasound (cystic structure in bladder), VCUG, CT/MRI.

Posterior Urethral Valves (PUV)

• Definition: Congenital obstructing membranous folds in the posterior urethra of boys.

• Impact: Most common cause of lower urinary tract obstruction in male infants. Causes bladder outlet obstruction.

• Complications:

  • Chronic kidney disease or renal failure.

  • Neurogenic-like bladder dysfunction.

  • Vesicoureteral reflux.

  • Pulmonary Hypoplasia: Results from fetal oligohydramnios in severe cases.

• Imaging Findings:

  • Prenatal: Thickened bladder wall and the "Keyhole Sign" (dilated posterior urethra).

  • Postnatal: Poor urinary stream, dribbling.

  • Gold Standard: Voiding cystourethrogram (VCUG) after birth.

• Management: Initial stabilization followed by endoscopic valve ablation.

Inflammatory Disorders

• Glomerulonephritis (GN):

  • Nonsuppurative inflammation of the glomeruli (filtering units).

  • Etiology: Antigen-antibody reaction, often following a hemolytic streptococci infection (respiratory or middle ear) or autoimmune disorder.

  • Nephritic Features: Hematuria ("cola-colored" urine), hypertension, oliguria, edema.

  • Nephrotic Features: Heavy proteinuria, hypoalbuminemia, hyperlipidemia, and edema.

  • Diagnosis: Urinalysis (RBC casts, proteinuria), Renal biopsy (Gold Standard).

  • Imaging: Ultrasound shows normal or enlarged kidneys in acute GN, but small/atrophied kidneys with increased cortical echogenicity in chronic stages.

• Pyelonephritis:

  • Bacterial (suppurative) infection of the renal parenchyma and pelvis, usually ascending from the lower tract.

  • Etiology: Most common organism is $Escherichia\,coli$.

  • Acute: Sudden fever, chills, flank pain, nausea, and CVA tenderness.

  • Chronic: Recurrent infection leading to renal scarring and calyx blunting.

  • Findings: Pyuria, bacteriuria, and WBC casts (upper UTI indicator).

  • Gold Standard: Contrast-enhanced CT (CECT) is the best for detecting complications like abscesses or scarring.

• Emphysematous Pyelonephritis (EPN):

  • Severe, necrotizing infection with gas formation within the kidney.

  • Status: Urologic emergency with high mortality.

  • Risk Factors: Diabetes mellitus is present in $\sim 80\text{--}90\%$ of cases.

  • Imaging: CT shows gas within the parenchyma. Ultrasound shows "dirty shadowing" from gas.

Renal Tuberculosis and Papillary Necrosis

• Renal Tuberculosis:

  • Extrapulmonary TB caused by hematogenous spread of $Mycobacterium\,tuberculosis$.

  • Findings: Granulomas in the cortex, sterile pyuria, ureteral strictures, bladder fibrosis ("thimble bladder").

  • Advanced Imaging: "Moth-eaten" appearance of calyces; "Putty kidney" (autonephrectomy/calcified nonfunctional kidney).

• Papillary Necrosis:

  • Ischemic necrosis of renal papillae associated with diabetes, analgesic abuse, and sickle cell anemia.

  • Imaging Findings:

    • Ring Sign: Contrast surrounding a sloughed papilla on CECT.

    • Golf Ball-on-tee Sign: Seen on IVU.

    • Lobster Claw Sign: Calyceal deformities.

• Cystitis:

  • Bladder inflammation (most commonly bacterial/$E.\,coli$).

  • Symptoms include dysuria (painful/burning sensation), urgency, and suprapubic discomfort.

  • Emphysematous Cystitis: Gas in the bladder wall, often in diabetics.

Urinary Calculi (Urolithiasis)

• Overview: Solid concretions of minerals and salts. Most common lodge at the ureterovesical junction or pelvic brim.

• Stones Types:

  • Calcium: Most common.

  • Uric Acid: Radiolucent on X-ray.

  • Struvite: Magnesium ammonium phosphate; associated with bacteria; forms Staghorn calculi.

• Presentation: Renal colic (severe flank pain radiating to groin), hematuria, nausea.

• Imaging: Non-contrast CT is the gold standard (highly sensitive for hyperdense stones). Ultrasound shows "Twinkling artifact" on Doppler.

• Staghorn Calculi: Large branching stones filling the renal pelvis and calyces. Usually composed of struvite.

Nephrocalcinosis and Obstruction

• Nephrocalcinosis: Diffuse deposition of calcium salts.

  • Medullary: Involves pyramids; associated with metabolic disorders.

  • Cortical: Usually from severe ischemia.

• Urinary Tract Obstruction:

  • Hydronephrosis: Dilation of the renal pelvicalyceal system.

  • Hydroureter: Dilation of the ureter.

  • Bilateral: Caused by blockage at or below the bladder (e.g., BPH).

  • Unilateral: Caused by blockage above the bladder level.

Renal Cysts and Polycystic Kidney Disease

• Renal Cysts: Fluid-filled sacs. Found in >50\% of individuals over age $50$.

  • Simple Cysts: Benign, thin-walled; no treatment needed.

  • Complex Cysts: May have septations or calcifications; classified via the Bosniak system for malignancy risk.

• Autosomal Dominant Polycystic Kidney Disease (ADPKD):

  • Manifests at ages $30\text{--}50$. Bilateral enlarged kidneys with numerous cysts.

  • Extrarenal Manifestations: Hepatic cysts, Berry Aneurysms (intracranial hemorrhage risk), cardiac valve abnormalities.

• Autosomal Recessive Polycystic Kidney Disease (ARPKD):

  • Presents in infancy; associated with hepatic fibrosis and respiratory distress.

Malignant Tumors

• Renal Cell Carcinoma (RCC):

  • AKA: Hypernephroma. Arises from renal tubular epithelium.

  • Triad: Hematuria, flank pain, palpable mass.

  • Metastasis: Most commonly to the lung.

  • Gold Standard: CT with contrast (enhancing solid mass).

• Wilms Tumor (Nephroblastoma):

  • Most common abdominal neoplasm in children (peak age $2\text{--}5$ years).

  • Associated with the $WT1$ gene mutation.

  • Presents as a painless abdominal mass.

• Bladder Carcinoma:

  • Most are Transitional Cell Carcinomas (TCC).

  • Primary Risk Factor: Cigarette smoking.

  • Classic Symptom: Painless gross hematuria.

  • Gold Standard: Cystoscopy (direct visualization and biopsy).

Renal Vascular and Failure Conditions

• Renal Vein Thrombosis (RVT):

  • Thrombus in renal vein causing congestion. Most common in severely dehydrated infants.

  • Adult associations: Nephrotic Syndrome and RCC invasion.

  • Imaging: Doppler Ultrasound is the initial modality.

• Acute Renal Failure (AKI):

  • Sudden GFR decline. Symptoms include oliguria and "fishy" breath odor.

  • Categories: Prerenal (decreased perfusion), Intrinsic (damage like ATN), Postrenal (obstruction).

• Chronic Renal Failure (CKD):

  • Progressive decline lasting $\ge 3$ months.

  • Leading Cause: Diabetes Mellitus.

  • Findings: Small atrophied kidneys (< 9\,cm length) with cortical thinning and increased echogenicity.

• Dialysis:

  • Hemodialysis: Blood passed through a dialyzer; requires vascular access (AV fistula/graft).

  • Peritoneal Dialysis: Peritoneal membrane acts as a filter.

    • CAPD: Manual, $3\text{--}5$ exchanges per day ($7$ days/week).

    • APD: Machine/cycler at night for $8\text{--}10$ hours.

  • Advantages of PD: Better hemodynamic stability (continuous fluid removal), no vascular access needed, helps preserve residual kidney function.