Postrenal Azotemia

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Contents 1 More Specific Terms 2 Introduction 3 Etiology 4 Pathology 5 Clinical-manifestations 6 Laboratory 7 Radiology 8 Management 9 More General Terms 10 Additional Terms 11 References

More Specific Terms

• abdominal compartment syndrome

Introduction

• Also see acute renal failure.

Etiology

• ureteral obstruction

• clot
• calculus
• sloughed papillae ( papillary necrosis)
• external compression

• tumor ( colon cancer)
• retroperitoneal fibrosis
• fecal impaction, especially in the elderly

• bladder outlet obstruction (98% of males)

• neurogenic bladder
• prostatic hypertrophy [3]
• carcinoma

• prostate cancer
• cervical cancer
• bladder cancer

• urinary calculus
• thrombus ( blood clot)
• urethral stricture
• phimosis
• fecal impaction, especially in the elderly

• bilateral renal vein occlusion ( thrombosis)
• surgery

• abdominal
• pelvic
• gynecologic

• radiation therapy

Pathology

• increased ureteral pressure proximal to site of obstruction may lead to irreversible renal damage
• obstruction must involve outflow tract of both kidneys (single kidney if other kidney is non functional) for azotemia

Clinical-manifestations

• flank pain
• abdominal pain
• nausea/vomiting
• anuria suggest complete obstruction
• oliguria, polyuria, or nocturia may accompany partial obstruction

Laboratory

• BUN/creatinine may be elevated secondary to increased tubular urea resorption
• check serum K+ for hyperkalemia with severe azotemia
• urinary indices & urinary Na+ are variable
• urine sediment is generally without significant cellular elements
• proteinuria is generally absent
• evaluation of serum & urine electrolytes with post- obstructive diuresis

Radiology

• renal ultrasound to delineate hydronephrosis
• computed tomography ( CT) may be helpful

• when results of ultrasound are equivocal
• retroperitoneal fibrosis
• periureteral metastatic disease

• anterograde or retrograde pyelography rarely used

Management

• relieve obstruction, monitor input & output - foley catheter
• fluid restriction if euvolemic or volume overloaded

• 1 to 1.5 L/day

• postobstructive diuresis may occur after relief of obstruction
• prognosis is good if obstruction is relieved within 1 week of onset, but tubular defects may persist
• little recovery may be exprected if high-grade obstruction exceeds 3 months

More General Terms

• azotemia
• urologic disease

Additional Terms

• acute renal failure (ARF)

References

1. Medical Knowledge Self Assessment Program (MKSAP) 11, 15, American College of Physicians, Philadelphia 1998, 2009
2. Harrison's Principles of Internal Medicine, 13th ed. Isselbacher et al (eds), McGraw-Hill Inc. NY, 1994, pg 1266
3. Prescriber's Letter 11(1):3 2004 Detail-Document#: [1] (subscription needed) [2]
4. National Guideline Clearinghouse Obstructive voiding symptoms secondary to prostate disease. (American College of Radiology) ngc-guideline: [3]
   - Treatment of urinary tract obstruction American College of Radiology ngc-guideline: [4]

postrenal azotemia; obstructive uropathy