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This chapter describes the effects of the natural methylxanthines caffeine and theophylline on kidney function. Theophylline in particular was used traditionally to increase urine out put until more potent diuretics became available in the middle of the last century. The mildly diuretic actions of both methylxanthines are mainly the result of inhibition of tubular fluid reabsorption along the renal proximal tubule. Based upon the use of specific adenosine receptor antagonists and the observation of a complete loss of diuresis in mice with targeted deletion of the A1AR gene, transport inhibition by methylxanthines is mediated mainly by antagonism of adenosine A1 receptors (A1AR) in the proximal tubule. Methylxanthines are weak renal vasodilators, and they act as competitive antagonists against adenosine-induced preglomerular vasoconstriction. Caffeine and theophylline stimulate the secretion of renin by inhibition of adenosine receptors and removal of the general inhibitory brake function of endogenous adenosine. Since enhanced intrarenal adenosine levels lead to reduced glomerular filtration rate in several pathological conditions theophylline has been tested for its therapeutic potential in the renal impairment following administration of nephrotoxic substances such as radiocontrast media, cisplatin, calcineurin inhibitors or following ischemia-reperfusion injury. In experimental animals functional improvements have been observed in all of these conditions, but available clinical data in humans are insufficient to affirm a definite therapeutic efficacy of methylxanthines in the prevention of nephrotoxic or postischemic renal injury. [ABSTRACT FROM AUTHOR]

The etiology of hematuria in the pediatric population is varied and ranges from infections, trauma, medical renal diseases, and urolithiasis, to congenital urologic conditions and, rarely, malignancies of the urinary tract. More often than not, hematuria in children is caused by medical rather than surgical processes. Hematuria may be characterized as microscopic or macroscopic (gross) and may be present with or without proteinuria. Although microscopic hematuria is much more common than macroscopic hematuria, the yield of an extensive work-up for isolated microscopic hematuria is low. Children with persistent isolated microhematuria should be evaluated with a urine Ca/Cr ratio, parental urinalysis, and annual renal function tests and blood pressure measurements to ensure that they do not develop hypertension or significant proteinuria. Children with gross hematuria should undergo a complete evaluation with CBC, serum C3 and C4, BUN, creatinine, potassium, ASO titers, coagulation parameters, and autoantibody titers such ANA, pANCA, cANCA, dsDNA, and anti-GBM in the setting of a relevant family history. Renal-bladder ultrasound is also recommended, along with renal biopsy for glomerulonephropathy. Invasive tests such as cystoscopy should be reserved for cases where the preceding work-up is inconclusive. Urologic referral is indicated when the work-up is suggestive of an anatomic abnormality, tumor, calculus, trauma, or recurrent macroscopic hematuria of undetermined origin. In contrast, the presence of hematuria in association with hypertension, proteinuria, hypocomplementemia, systemic disease, or a family history of renal disease almost always warrants referral to a nephrologist. [ABSTRACT FROM AUTHOR]

Diabetic nephropathy (DN) is the leading cause of chronic kidney disease and end-stage renal disease (ESRD). Patients with diabetic nephropathy have a high burden of cardiovascular morbidity and mortality. Therefore, interventions that reduce the incidence and progression rate of DN will reduce morbidity and mortality rates as well as health care costs. Hyperglycemia and arterial hypertension are the two main risk factors for DN, but even in the presence of hyperglycemia and elevated blood pressure (BP) for long periods, DN develops only in susceptible patients. Family studies have confirmed the presence of hereditary factors in the development of DN. Besides these four key factors, others have also been implicated, although their impact is less relevant. A systematic approach aiming at prompt diagnosis and intervention can reduce the incidence of DN and slow progression toward ESRD [ABSTRACT FROM AUTHOR]

The kidney is one of the most frequently affected organs in several types of systemic amyloidosis. Amyloid nephropathy is diagnosed by Congo red positivity of kidney tissue and by the presence of non-branching, randomly oriented fibrils that are 8–12 nm in diameter and evident by electron microscopy. Amyloid deposits can occur in the mesangium, glomerular capillary loops, tubulo-interstitium, and/or vasculature of the kidney. Amyloid nephropathy is typically characterized by nephrotic syndrome and progression to end-stage renal disease. The rate of decline in kidney function is variable and can be slowed by treatments that reduce the production of amyloidogenic precursor proteins or new amyloid deposits. [ABSTRACT FROM AUTHOR]