6.3 Renal & Urinary Assessment & Disorders

Renal Assessment and Laboratory Interpretation

Renal assessment begins with history (voiding patterns, fluid intake, medications) and physical findings. Flank or costovertebral angle (CVA) tenderness suggests pyelonephritis or obstructing stones — percuss gently because an inflamed kidney is exquisitely tender. Palpate and percuss for bladder distension above the symphysis pubis in retention. Assess urine characteristics: color, clarity, and odor. Cloudy, foul-smelling urine suggests infection; cola-colored urine suggests glomerular bleeding; dilute pale urine in large volumes suggests concentrating defects or diabetes insipidus.

Strict intake and output (I&O) is essential. The minimum acceptable urine output is 30 mL per hour (0.5 mL/kg/hr) — sustained output below that requires provider notification. Daily weights (same time, same scale, same clothing) are the most reliable fluid status measure: 1 kg equals roughly 1 liter of fluid. Check for dependent and periorbital edema and monitor blood pressure, since the kidneys regulate both volume and renin-mediated pressure.

Key laboratory values:

Urinary casts localize disease: red cell casts indicate glomerulonephritis, white cell casts indicate pyelonephritis or interstitial nephritis, and muddy brown granular casts indicate acute tubular necrosis.

Urinary Tract Infection and Pyelonephritis

A urinary tract infection (UTI) presents with dysuria, frequency, urgency, suprapubic discomfort, and cloudy, foul-smelling urine. In older adults, new confusion may be the only sign. Obtain a clean-catch or catheterized urine culture before starting antibiotics, then begin empiric therapy per culture results. Encourage fluids (2 to 3 liters daily unless contraindicated) to flush the urinary tract.

Pyelonephritis is infection of the kidney itself: fever, chills, flank pain, CVA tenderness, nausea and vomiting, plus lower urinary symptoms. It carries a risk of urosepsis — monitor temperature, heart rate, blood pressure, and lactate, and escalate for hypotension or worsening mental status. Treatment is culture-directed antibiotics; severe cases require hospitalization and IV therapy.

Urolithiasis (Kidney Stones)

Stones cause sudden, severe, colicky flank pain radiating to the groin, with hematuria, nausea, and restlessness — patients cannot find a comfortable position. A signature nursing action is to strain all urine and send any recovered stone for chemical analysis, since prevention depends on stone type:

• Calcium oxalate — the most common type (about 75 to 80%). Limit high-oxalate foods (spinach, rhubarb, chocolate, nuts, tea), but do not restrict dietary calcium, which binds oxalate in the gut.
• Struvite (magnesium ammonium phosphate) — associated with chronic UTIs; forms staghorn calculi; treat the infection.
• Uric acid — associated with gout and acidic urine; alkalinize the urine and use allopurinol; limit purines.
• Cystine — rare, genetic; requires high fluid intake and urine alkalinization.

Acute management: hydration to promote a urine output of 3 to 4 liters per day, NSAID analgesia, and an alpha-blocker such as tamsulosin as medical expulsive therapy. Larger or obstructing stones may need extracorporeal shock wave lithotripsy, ureteroscopy, or percutaneous nephrolithotomy. Fever with an obstructing stone is a urologic emergency.

BPH and Urinary Retention

Benign prostatic hyperplasia (BPH) compresses the urethra, producing hesitancy, weak stream, dribbling, frequency, nocturia, and eventually acute urinary retention. Medications include alpha-1 blockers (tamsulosin, doxazosin) that relax prostatic smooth muscle — teach patients about orthostatic hypotension and to rise slowly, especially after the first dose — and 5-alpha reductase inhibitors (finasteride), which shrink the gland over months and must not be handled by pregnant people.

For retention, catheterization relieves the obstruction; decompression of very large volumes should be monitored for post-obstructive diuresis and hematuria. After transurethral resection of the prostate (TURP), expect continuous bladder irrigation (CBI): outflow should be light pink; bright red drainage with clots indicates hemorrhage — increase the CBI rate as ordered and notify the surgeon. Track irrigant versus output carefully to detect clot retention, and teach the patient to avoid straining at stool (prescribe stool softeners) and heavy lifting during recovery.

Glomerulonephritis Versus Nephrotic Syndrome

These two glomerular patterns are a classic exam contrast:

Post-streptococcal glomerulonephritis follows a group A strep pharyngitis or skin infection by 1 to 3 weeks; expect elevated antistreptolysin O titers and low complement C3. Nursing care: monitor I&O and daily weights, restrict sodium and fluids during the oliguric phase, and manage hypertension.

Bladder Scanners, Catheters, and CAUTI Prevention

A bladder scanner noninvasively estimates post-void residual; retention volumes above roughly 300 to 500 mL typically trigger straight catheterization per protocol — scanning first avoids unnecessary catheterization. Catheter-associated urinary tract infection (CAUTI) is one of the most common hospital-acquired infections; prevention bundle: insert only for appropriate indications using aseptic technique, maintain a closed drainage system, secure the catheter to prevent traction, keep the collection bag below bladder level and off the floor without kinking, perform routine perineal care, sample urine only from the sampling port, and remove the catheter as early as possible using nurse-driven removal protocols.