0071643192.pdf

RENAL AND GENITOURINARY

EMERGENCIES

DIAGNOSIS

■ BUN/Cr ratio > 10:1.
■ Evidence of increased renal Na+conservation:
■ Urinary Na+(UNa) concentration < 20 mEq/dL.
■ Fractional excretion of sodium (FENa) < 1%.

FENa=

Urine Na ×Plasma Cr

× 100

Plasma Na ×Urine Cr

■ May be impaired in patients with chronic renal failure (CRF) or diuretic
use
■ Increased urine osmolality
■ Urinalysis: Normal with occasional hyaline casts
■ No evidence for obstruction on renal ultrasound

TREATMENT

■ Treat underlying cause (eg, correct hypovolemia, augment cardiac output).
■ Discontinue offending drugs: NSAIDs, ACE inhibitors.
■ Correct electrolyte imbalances.
■ Dialyze as needed.

Intrinsic

Intrinsic acute renal failure results from pathology of the glomerulus, intersti-
tium, or renal tubule.

CAUSES

Causes of intrinsic ARF include:

■ Glomerulonephritis
■ Acute interstitial nephritis
■ Acute tubular necrosis
■ Vascular disease

GLOMERULONEPHRITIS

Glomerulonephritis is a renal disease characterized by inflammation of the
glomeruli. It may be a primary process, as in poststreptococcal glomu-
lonephritis, or secondary to underlying systemic disease, such as lupus,
Goodpasture syndrome, and systemic vasculitis. Most cases are seen in the
pediatric population.

SYMPTOMS/EXAM

■ Patients may be asymptomatic at time of diagnosis.
■ Symptoms include dark urine, hematuria, edema, hypertension.

DIAGNOSIS

■ The characteristic findings on urinalysis include hematuria, dysmorphic
RBCs, proteinuria, and, most importantly, RBC casts.
■ Proteinuria may be nephrotic range.
■ Renal biopsy is definitive.

A low UNaindicates intact

urinary concentrating ability

and the presence of a stimulus

to conserve Na+.

Evaluating urinary sodium

indices is not helpful in

patients with underlying

chronic renal failure or

diuretic use.