Kidney Function

C1q nephropathy is a rare kidney disease that can present with nephrotic syndrome and typically has the histologic phenotype of either minimal change disease or focal segmental glomerulosclerosis (FSGS). Disagreement exists about whether it is a distinct immune complex–mediated glomerulopathy or it resides in the spectrum of FSGS-minimal change disease. Two African American patients with C1q nephropathy histologically presenting as the collapsing variant of FSGS (collapsing C1q nephropathy) and rapid loss of kidney function were genotyped for polymorphisms in the non–muscle myosin heavy chain 9 gene (MYH9). Both cases were homozygous for the MYH9 E1 risk haplotype, the variant strongly associated with idiopathic FSGS, collapsing FSGS in human immunodeficiency virus–associated nephropathy, and focal global glomerulosclerosis (historically attributed to hypertensive nephrosclerosis). Collapsing C1q nephropathy with rapid progression to end-stage renal disease appears to reside in the MYH9-associated disease spectrum.

Biocompatibility of a dialyzer membrane has been defined largely by the degree to which it activates complement. Modifications of the cellulose membrane and the development of synthetic membranes have minimized the activation of complement and its associated complications. However, less is known about the blood–dialyzer membrane interactions that may occur in membranes made of the same synthetic polymer. A patient is described who developed dialysis-associated thrombocytopenia using a Fresenius Medical Care Optiflux polysulfone membrane (F-160) that significantly improved when switched to the polysulfone Asahi REXEED 25S membrane (AR-25S). A comparison of postdialysis d-dimer level suggests that the F-160 membrane activated the coagulation pathway to a greater extent than the AR-25S. Subtle differences between the internal surfaces of the membranes that are manufacturer specific may be responsible for exposing this patient's unique predisposition to thrombosis and thrombocytopenia. Despite the advances in membrane biocompatibility, differences may exist among membranes made of the same synthetic polymer.

Background: Reports of culture-negative peritoneal dialysis (PD)-associated peritonitis have been sparse, conflicting, and limited to small single-center studies. The aim of this investigation is to examine the frequency, predictors, treatment, and outcomes of culture-negative PD-associated peritonitis.Study Design: Observational cohort study using Australia and New Zealand Dialysis and Transplant Registry (ANZDATA) data.Setting & Participants: All Australian PD patients between October 1, 2003, and December 31, 2006.Predictors: Demographic, clinical, and facility variables.Outcomes & Measurements: Culture-negative PD-associated peritonitis occurrence, relapse, hospitalization, catheter removal, hemodialysis transfer, and death.Results: Of 4,675 patients who received PD in Australia during the study period, 435 episodes of culture-negative peritonitis occurred in 361 individuals. Culture-negative peritonitis was not associated with demographic or clinical variables. A history of previous antibiotic treatment for peritonitis was more common with culture-negative than culture-positive peritonitis (42% vs 35%; P = 0.01). Compared with culture-positive peritonitis, culture-negative peritonitis was significantly more likely to be cured using antibiotics alone (77% vs 66%; P < 0.001) and less likely to be complicated by hospitalization (60% vs 71%; P < 0.001), catheter removal (12% vs 23%; P < 0.001), permanent hemodialysis therapy transfer (10% vs 19%; P < 0.001), or death (1% vs 2.5%; P = 0.04). Relapse rates were similar between the 2 groups. Patients with relapsed culture-negative peritonitis were more likely to have their catheters removed (29% vs 10% [P < 0.001]; OR, 3.83; 95% CI, 2.00-7.32). Administration of vancomycin or cephalosporin in the initial empiric antibiotic regimen and the timing of catheter removal were not significantly associated with clinical outcomes.Limitations: Limited covariate adjustment. Residual confounding and coding bias could not be excluded.Conclusions: Culture-negative peritonitis is a common complication with a relatively benign outcome. A history of previous antibiotic treatment is a significant risk factor for this condition.