Academic journal article International Public Health Journal

Tropical Nephrology

Academic journal article International Public Health Journal

Tropical Nephrology

Article excerpt

Introduction

Tropical nephrology encompasses a broad spectrum of pathologic changes of the kidney in response to infectious organisms, natural toxins, or environmental toxins specific to that region of the world between the tropic of cancer and the tropic of capricorn. In addition, tropical nephrology must also account for the spectrum of primary glomerular diseases that are also observed in western countries. In fact, primary glomerular diseases including IgA nephropathy, IgM nephropathy, membranous nephropathy, and lupus nephritis, have been reported to have a prevalence in the tropics of 2.5 times that of the western world (1).

Clinical syndromes can range from asymptomatic hematuria or proteinuria, to self-limited episodes of acute kidney injury, or to progressive chronic glomerulonephritis that persists despite eradication of the offending organism. The host's immune response and subsequent inflammatory process play a critical role in the renal lesions observed. Treatment is often directed at the offending pathogen, with little benefit observed from immunosuppression directed at the resultant inflammatory process in most cases.

Clinical syndromes

Clinical syndromes observed include asymptomatic urine abnormalities, macroscopic hematuria, acute kidney injury, and glomerular disease. Glomerular disease may be primary or secondary to a variety of infectious organisms.

Nonspecific urinary sediment changes are often observed in the setting of febrile infectious diseases. These include microscopic hematuria, proteinuria, pyuria, or the presence of granular casts. Usually these changes resolve as the disease improves. Proteinuria can range from mild and transient to severe and persistent despite treatment of the offending pathogen.

Transient proteinuria often less than 1gram per 24 hours can be seen in any acute febrile illness as well as in the setting of dehydration, intense exercise, or severe emotional stress. Orthostatic proteinuria, which can be diagnosed with a split urine collection, should also be considered in the adolescent population with less than 1 gram per 24 hours, although its occurrence in the tropical region is unclear. Proteinuria of over 1 gram and especially over 2 grams per 24 hours that persists beyond 4 weeks suggests a glomerular cause.

Macroscopic hematuria is often suspected in setting of red to brown urine. It should be noted that hemoglobinuria and myoglobinuria can also present similarly. When possible a centrifugation of a fresh urine sample should be performed. If the red/brown color is limited to the sediment with a clear supernatant, then hematuria is responsible. However, if the supernatant is a red/brown color, it should be tested and if heme positive, then either hemoglobinuria or myoglobinuria should be suspected. It is important to study a fresh sample of urine, as red blood cells may lyse with prolonged standing and result in a false positive heme test of the supernatant (2).

The differential diagnosis of macroscopic hematuria observed in the tropics should include schistosomiasis as well as bacterial infection, but should also take into consideration IgA nephropathy, post-streptococcal glomerulonephritis, trauma, nephrolithiasis, sickle cell disease, and malignancy. Schistosomiasis affecting the lower urinary tract typically presents with painful terminal gross hematuria and will be discussed in detail below. Gross hematuria that occurs within one to three days of an upper respiratory infection ("synpharyngitic hematuria") suggests the diagnosis of IgA nephropathy. Gross hematuria that occurs 10-21 days after an episode of pharyngitis or cellulitis suggests the diagnosis of post-streptococcal glomerulonephritis.

Hemoglobinuria is a common finding in tropical diseases and often a result of intravascular hemolysis. Significant intravascular hemolysis has been documented after viper bites as well as after wasp or hornet stings (3-7). In addition, glucose 6 phosphate dehydrogenase deficiency is common in tropical countries and may account for episodes of intravascular hemolysis after infection or exposure to certain medications (1). …

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