Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (243 page)

   Secondary hyperoxaluria may also be precipitated by the chronic ingestion of oxalate precursors (e.g., ascorbic acid) or of foods rich in oxalic acid (e.g., rhubarb, parsley, cocoa, nuts, or star fruit [carambola]).

   Who Should Be Suspected?

   PH type 1: The age range at diagnosis varies from <1 to >50.

   Infants (26% of PH type 1 cases) are generally diagnosed younger than 6 months of age with nephrocalcinosis (91%), failure to thrive (22%), urinary tract infection (21%), and end-stage renal disease (ERSD, 14%).

   Those diagnosed in childhood generally present with symptoms of recurrent urolithiasis and rapidly declining renal function (30%), that is, renal colic, hematuria, and urinary tract infection, although a few will have bilateral obstruction and acute renal failure.

   Adults are diagnosed either by the occasional calculus formation (30%) or only after failed isolated renal transplant (10%).

   Laboratory Findings

   Urinary oxalate: PH type 1 or 2, usually >100 mg/24 hours unless renal function is diminished; secondary disease, usually 50–100 mg/24 hours.

   Molecular genetic testing (PH type 1): Demonstrates the mutation of the alanine:glyoxylate aminotransferase (AGXT) gene.

Suggested Readings

Hoppe B. An update on primary hyperoxaluria.
Nat Rev Nephrol.
2012;8:467–475.

Hoppe B, Leumann E, von Unruh G, et al. Diagnostic and therapeutic approaches in patients with secondary hyperoxaluria.
Front Biosci.
2003;8:e437–e443.

PRIAPISM

   Definition

   Priapism is a persistent erection of the penis (or clitoris), lasting at least 4 hours, that is not associated with sexual stimulation or desire. This relatively rare condition can occur in all age groups (although it exhibits a bimodal peak distribution of incidence at ages 5–10 and 20–50) and is especially common in those with sickle cell disease. Classified as either ischemic or nonischemic, ischemic priapism is a urologic emergency, whereas nonischemic priapism is usually self-limited.

   Ischemic (low flow, anoxic, or venoocclusive) priapism is the most common form of the condition. The prolonged nitric oxide–mediated relaxation and paralysis of cavernosal smooth muscle results in a compartment syndrome with increasing hypoxia and acidosis in the cavernous tissue. Structural damage to the erectile tissue is believed to occur at the microscopic level as early as 4–6 hours after the onset of the erection, with significant structural changes in the cavernous smooth muscle after 12 hours and irreversible damage as early as 24 hours after onset.