Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (14 page)

   
Campylobacter
, especially
Campylobacter jejuni
.

   
Clostridium difficile
.

   Possibly other organisms (e.g., HIV,
Escherichia coli
,
Mycoplasma genitalium
).

   HLA-B27 is positive in approximately half of the patients and seems to be associated with a more sudden and severe onset of symptoms as well as increased likelihood to have chronic (long-lasting) disease.

   Elevated ESR and CRP during the acute phase of disease.

   RF is negative.

   Synovial fluid analysis shows elevated WBC count, predominantly neutrophils, and may help distinguish reactive arthritis from other forms of arthritis.

RETROPERITONEAL FIBROSIS

   Definition

   A rare disease characterized by the presence of fibrosclerotic tissue in the retroperitoneum, often leading to encasement of the ureters and, less frequently, blood and lymphatic vessels.

   About two thirds of the cases are idiopathic, while the remaining cases are secondary to a variety of causes, including drugs (e.g., beta-blockers, methyldopa, hydralazine, analgesics), tumors (e.g., Hodgkin disease and non-Hodgkin lymphoma, sarcomas, carcinomas), infections (e.g., TB, histoplasmosis, actinomycosis), radiation, or surgery.

   Idiopathic retroperitoneal fibrosis is part of the disease spectrum of chronic periaortitis, which is characterized by inflammation and fibrosis surrounding the aorta and iliac arteries. It has also been suggested that idiopathic retroperitoneal fibrosis is a manifestation of either a systemic autoimmune disorder or IgG4-related disease.

   Who Should Be Suspected?

   Most patients present with abdominal, lower back, or flank pain. In addition, up to one half of patients complain of constitutional manifestations such as fever, weight loss, fatigue, and night sweats. Renal failure due to obstruction of the ureters develops in more than 40% of patients, and newonset hypertension has been reported in approximately one third of patients.