Edmund Bourke

The role of ureagenesis in pH homeostasis

Abstract Catabolism of protein liberates HCO 3 − , which cannot be eliminated in the necessary amounts through the lungs, kidneys, or intestines, and thus poses a threat of alkalosis to air-breathing animals. That threat is met by biosynthetic sequences that consume the weak acid NH 4 + and liberate its proton for reaction with HCO 3 − . Different kinds of air-breathing animals use different syntheses for this purpose; mammals utilize ureagenesis. Modulation of the rate of urea synthesis in response to pH is an important part of the interacting regulatory systems by which pH homeostasis is maintained in mammals.

Comparison of Fine-Needle Aspiration Biopsy, Doppler Ultrasound, and Radionuclide Scintigraphy in the Diagnosis of Acute Allograft Dysfunction in Renal Transplant Recipients: Sensitivity, Specificity, and Cost Analysis

150 episodes of allograft dysfunction in 128 renal transplant recipients, 77 due to acute rejection, 32 secondary to acute-on-chronic rejection, 33 due to either prerenal factors, acute tubular necrosis, or ciclosporin A nephrotoxicity, and 8 secondary to multiple causes, were evaluated by fine-needle aspiration biopsy (FNAB), Doppler ultrasound (DUS), and radionuclide scintigraphy (RS), each performed within a 24-hour period and prior to any specific therapeutic intervention. Tests were interpreted by appropriate specialists in a large transplant center without access to clinical information. The final diagnosis was based primarily upon response to therapeutic maneuvers with histological (core biopsy) confirmation in 123 episodes. RS was the most sensitive (70%) test for the diagnosis of acute rejection during the early posttransplant period, exceeding both FNAB (52%) and DUS (43%). The predictive accuracy of either FNAB, DUS, RS, or core biopsy in the detection of a steroid-responsive component to acute rejection when superimposed upon chronic rejection was low at approximately 50%. When the underlying cause of renal dysfunction was either prerenal, acute tubular necrosis, or ciclosporin A nephrotoxicity, FNAB, DUS, and RS each gave an erroneous diagnosis of acute rejection in about 50% of the episodes. Cost analysis revealed that core biopsy was the most expensive test, but only 9% more than RS, with FNAB the least costly. In conclusion, the lack of ideal sensitivity and specificity combined with the expense of present-day FNAB, DUS, RS, and core biopsy in the diagnosis of a therapeutically reversible component to acute-on-chronic rejection and of FNAB, DUS, and RS in the diagnosis of acute rejection during the early posttransplant period should prompt research into ways to improve their diagnostic yield or alternate modalities.

Naproxen-Induced Nephropathy in Systemic Lupus erythematosus

A 34-year-old female with an 8-month history of systemic lupus erythematosus and intermittent naproxen use presented with acute oliguric renal failure, hypoalbuminemia, 4+ proteinuria, and an active urinary sediment. The clinical picture suggested a rapidly progressive lupus glomerulonephritis. Renal biopsy, however, demonstrated chronic, active interstitial nephritis without evidence of immune deposits by immunofluorescence or electron microscopy. Nonsclerotic glomeruli revealed diffuse foot process fusion without cellular proliferation. These findings were consistent with nonsteroidal anti-inflammatory drug induced nephropathy. Discontinuation of naproxen and institution of corticosteroid therapy was followed by improvement in renal function and remission of nephrotic syndrome. This case represents the first report of nonsteroidal antiinflammatory drug nephropathy associated with systemic lupus erythematosus.

Indomethacin in Streptozocin-Induced Nephrogenic Diabetes Insipidus

A 14-year-old female patient with metastatic carcinoid developed streptozocin-induced glomerular, proximal, and distal tubular dysfunction. The latter was in the form of nephrogenic diabetes insipidus, with urine volumes in excess of 11 L/24 h. The prostaglandin synthetase inhibitor, indomethacin, rapidly corrected the polyuria both initially and on rechallenge, independent of change in glomerular filtration rate.

Mesangial Glomerulonephropathy with Decreased Circulating C4 and Predominant Mesangial C4 Deposition in Association with One Null Gene at the C4B Locus

We report a case of mesangial glomerulonephropathy associated with decreased circulating C4 in a young man with recurrent microscopic hematuria and one null gene at the C4B locus. Mesangial deposits moderately reactive with anti-C4 and weakly reactive with anti-C3 and anti-IgA were found on renal biopsy. No evidence was found to support a diagnosis of IgA nephropathy or any other of the recently described mesangial glomerulonephropathies with immunoglobulin and complement deposition. This case apparently represents a unique, heretofore undescribed variant of mesangial glomerulonephropathy associated with mesangial C4 deposition and C4 hypocomplementemia.