Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (245 page)

   Cavernous blood gas analysis and/or Doppler ultrasonography can be used to distinguish immediately ischemic from nonischemic priapism persisting longer than 4 hours.

   A volume of 3–5 mL is aspirated with a 19- to 21-gauge needle from one side of the corpus cavernosum.

   The color of ischemic blood will be black, and blood gas analysis will reveal hypoxia, hypercarbia, and acidemia.

   The color of nonischemic blood will be red, and blood gas analysis will reveal normal levels of oxygen, carbon dioxide, and pH.

Suggested Readings

Burnett AL, Bivalacqua TJ. Priapism: current principles and practice.
Urol Clin North Am.
2007;34:631–642.

Cherian J, Rao AR, Thwaini A, et al. Medical and surgical management of priapism.
Postgrad Med J.
2006;82:89–94.

RETROPERITONEAL FIBROSIS

   Definition

   Retroperitoneal fibrosis (formerly Ormond disease) is a rare condition (incidence of 0.1–1.3 per 100,000 for the idiopathic form) characterized by the proliferation of inflammatory and fibrous tissue in the retroperitoneum, often encasing the ureters or abdominal organs and resulting in ureteral blockage.

   The disorder occurs primarily (70% of cases) in idiopathic form among individuals at age 40–60 (70%). There are also secondary forms of the disorder with a variety of identified causes (certain drugs, malignancies, infections, radiation therapy, retroperitoneal hemorrhage, and surgical sequelae).

   The pathogenesis of the disorder is unclear, but two leading theories suggest (each with some evidence) either an exaggerated local inflammatory reaction to aortic atherosclerosis (incited by oxidized low-density lipoprotein) or a manifestation of systemic autoimmune disease.

   Who Should Be Suspected?

   Compiling the data from four studies, the most common presenting symptoms are pain in the lower back, abdomen, and/or flank (28–90%); testicular pain (50–64%); fatigue (60%); substantial weight loss (54%); and newonset hypertension (33–57%). Urinary symptoms (urgency, frequency, and dysuria) are also common. Most patients have renal impairment by the time they are seen for medical attention.

   Laboratory Findings

   The diagnostic method of choice is a contrast-enhanced CT scan to visualize the extent of fibrosis, to assess the presence of lymphadenopathy and tumors, and to enable guided biopsy for tissue analysis.