Peritoneal macrophages (PMC) from patients undergoing continuous ambulatory peritoneal dialysis (CAPD) were compared to peritoneal macrophages from healthy volunteers and to peripheral blood monocytes (PBM) from CAPD patients, hemodialysis patients, and healthy volunteers. PMC from CAPD patients had morphology similar to PMC and PBM from healthy volunteers. HLA-DR antigen and Fc receptors were present on the cell surface. These monocytes had similar sequential morphologic changes in long-term culture compared to PBM from healthy volunteers. Phagocytosis, hydrogen peroxide generation and bactericidal activity were the same in PMC from CAPD patients as in PBM from healthy volunteers. Chemotaxis and eicosanoid precursor uptake studies suggest that PMC from CAPD patients may be relatively immature bone-marrow-derived cells. Although these cells function well as phagocytes, further study is warranted to define their immune competence, many components of which develop during differentiation into mature macrophages and may therefore be deficient in patients undergoing CAPD.

The syndrome of inappropriate antidiuretic hormone secretion (SIADH) as a cause of hypotonic hyponatremia is well recognized. The syndrome is commonly associated with cranial and thoracic infectious disease or malignancy. An idiopathic form of the syndrome has been reported, but poorly documented. Our patient, an 88-year-old man without any associated disease, had SIADH confirmed by a standard water load test. The pattern of antidiuretic hormone release corresponded to the "vasopressin leak" pattern. A review of ten cases of "idiopathic" SIADH showed that each of these cases has been associated with neuropsychiatric or other medical disturbances. We conclude that idiopathic inappropriate antidiuresis does exist and is a discrete category of SIADH. Data suggest that advanced age may be a risk factor for this disease. This syndrome may account for the increased susceptibility to hyponatremia among older patients.

We investigated the role of the opsonic glycoprotein fibronectin in the host defense of the peritoneum in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Fibronectin concentration in peritoneal dialysate from high infection rate CAPD patients (greater than 1.50 episodes peritonitis per year) was significantly less than from low infection rate CAPD patients (less than 0.55 episodes peritonitis per year). In vitro secretion of fibronectin by cultured peritoneal macrophages from patients with high infection rate was less than from low infection rate patients (P less than 0.05) and controls (P less than 0.01). In vitro secretion of the second component of complement, however, was similar in both high and low infection rate patients. Plasma fibronectin concentration and in vitro fibronectin secretion by cultured peripheral blood monocytes was not different between high infection rate patients and low infection rate patients, but was less than normals. Decreased fibronectin secretion by peritoneal macrophages is associated with a higher incidence of peritonitis among CAPD patients.

Infectious complications in the renal transplant patient are common, and infecting agents include opportunistic organisms as well as common pathogens. However, we were only able to document 6 patients who had septic arthritis from more than 800 who received a renal transplant at our institution over an 18‐year period. Furthermore, only 16 other cases of infectious arthritis have been reported in the literature. All of our patients had an apparent predisposing factor and 3 patients had prior infection with the same organism. The knee was the most commonly infected joint. The initial synovial fluid white blood cell count was usually > 30,000 cells/mm3, but 1 patient with viral arthritis initially had noninflammatory fluid. The peripheral blood white blood cell count may not be elevated. All of our cases of initial joint infection occurred by 18 months posttransplant. Blood cultures were positive in 3 of 4 patients with bacterial infection. Followup of these 6 patients averaged 4.3 years. Numerous other rheumatologic syndromes and disorders peculiar to the posttransplant period may mimic a septic joint. Consequently, despite the low frequency of occurrence of septic arthritis, persistent attention to the locomotor system in the transplant patient is warranted.

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