Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (235 page)

   A history and physical examination should include a digital rectal examination of the prostate. A urine culture and urinalysis for hematuria should be undertaken to rule out other or more serious disorders that could cause symptoms similar to those of BPH (urinary tract infection, bladder calculi, prostatitis, prostate cancer, or bladder cancer). On digital rectal examination, symmetric enlargement and firmness of the prostate are typical of BPH, whereas asymmetric areas are suggestive of prostate cancer.

   Laboratory Findings

   Serum prostate-specific antigen (PSA): In 20% of BPH patients, serum PSA may be increased from the widely used prostate cancer cutoff value of 4.0– 10 ng/mL. In fact, BPH is a more common cause of elevated PSA levels than is prostate cancer.

   Serum creatinine: While not recommended by the American Urological Association in the management of patients with BPH, a high serum creatinine value may suggest a bladder outlet obstruction or underlying renal or prerenal disease and an increased risk for post–prostate surgery complications and mortality.

Suggested Readings

Barry MJ, Fowler FJ Jr, O’Leary MP, et al. The American Urological Association symptom index for benign prostatic hyperplasia. The Measurement Committee of the American Urological Association.
J Urol.
1992;148:1549–1557.

Jacobsen SJ, Girman CJ, Lieber MM. Natural history of benign prostatic hyperplasia.
Urology.
2001;58:5–16.

Madersbacher S, Alivizatos G, Nordling J, et al. EAU 2004 guidelines on assessment, therapy and follow-up of men with lower urinary tract symptoms suggestive of benign prostatic obstruction (BPH guidelines).
Eur Urol.
2004;46:547–554.

CALCULI

   Definition

   A renal calculus (kidney stone) is a solid concretion/crystalline aggregate formed in the kidneys by supersaturation of dietary minerals in the urine, one or more of which nucleate seed crystals. Both the supersaturation and the crystalline aggregation processes are pH dependent.

   Calculi can be classified by their location and chemical composition.

   Locations include the kidney (nephrolithiasis), ureter (ureterolithiasis), or bladder (cystolithiasis).

   Varieties of chemical composition include calcium containing (primarily calcium oxalate but also calcium phosphate); struvite (magnesium ammonium phosphate); uric acid; and cystine.

   Calcium oxalate or calcium phosphate calculi occur in 85% of male and 70% of female patients. Calcium oxalate crystals require an acid environment. Calcium phosphate crystals occur with hypercalciuria, hypocitraturia, and an alkaline environment (Figure
7-1
). A comparison of idiopathic causes of hypercalciuria is presented in Table
7-1
.

   Struvite stones (staghorn calculi), occurring in 10–15% of patients, are generated by UTI urea-splitting bacteria, including
Proteus
species (>50% of cases; after ruling out
Klebsiella
,
Pseudomonas
,
Serratia
, and
Enterobacter
), and in patients with persistently alkaline urine. Although not producing symptoms unless inducing urinary tract obstruction or infection, this type of calculus can lead to renal failure over years if present bilaterally. Staghorn calculi should be cultured.