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Course of acute renal failure studied by a model of creatinine kinetics. A computerized model of creatinine kinetics was developed to predict the relationship between creatinine clearance [G(t)] and plasma creatinine concentration [C(t)] in patients with postischemic acute renal failure (ARF). A comparison of predicted to measured values in 35 episodes of ARF in 27 patients revealed three patterns of declining G(t) following an ischemic insult. Pattern A, characterized by an abrupt step decrement in G(t) following an isolated renal ischemic episode lasting minutes or hours, was observed in nine patients. It was followed invariably by an immediate ramp increment in G(t), despite which C(t) continued to increase for several days. Urinary indices during the period of increasing azotemia were consistent with the resolving stage of ARF. Patterns B (N = 15) and C (N = 11) were associated with persistent renal ischemia of long (days to weeks) duration and were respectively characterized by prolonged ramp or exponential decrements in G(t). A concurrent increase in C(t) was associated with urinary indices typical of the maintenance or sustained stage of ARF. Recovery of G(t) was observed in only two-thirds of patterns B and C cases and took the form of a ramp or exponential increment. Because G(t) and total body water were changing rapidly in ARF, changes in measured plasma creatinine levels alone failed to identify these patterns of deteriorating or improving renal function. However, when the computerized model was used in conjunction with daily measured values of C(t) and body weight and occasional estimates of G(t), the course and prognosis of ARF in individual patients were illuminated. L'evolution d'une insuffisance renale aigue etudiee par un modele de cinetique de la creatinine. Un modele sur ordinateur de cinetique de la creatinine a ete developpe afin de predire la relation entre la clearance de la creatinine [G(t)] et la creatininemie [C(t)] chez les malades ayant une insuffisance renale chronique post-ischemique (ARF). Une comparaison des valeurs predites avec celles measurees dans 35 episodes d ARF chez 27 malades a revele trois types de declin de G(t) apres une atteinte ischemique. Le type A, caracterise par un decrochement abrupt de G(t) suivant un episode isole d'ischemie renale durant quelques minutes ou heures, a ete observe chez neuf malades. Il etait suivi invariablement par une augmentation lineaire immediate de G(t), bien que C(t) continue a s'elever pendant plusiers jours. Les parametres urinaires pendant la periode d'azotemie croissante etaient compatibles avec le stade de guerison de l'ARF. Les types B(N = 15) et C (N = 11) etaient associes a une ischemie renale persistante de longue duree (plusiers jours ou semaines) et etaient caracterises respectivement par des decroissances prolongees lineaires ou exponentielles de G(t). Une augmentation concomitante de C(t) etait associee avec des index urinaires typiques d'un stade d'entretien ou de prolongation de l'ARF. Une recuperation de G(t) etait observee chez seulement les deux tiers des cas de types B et C et prenait la forme d'une augmentation lineaire ou exponentielle. Puisque G(t) et l'eau totale de l'organisme changeaient rapidement en ARF, les modifications de la concentration de creatinine plasmatique ne pouvaient pas, a elles seules, tradiure la deterioration ou l'amelioration de la fonction renale. Cependant, lorsque le modele par ordinateur etait utilise en association aux valeurs mesurees journalieres de C(t) et de poids corporel et a des estimations occasionnelles de G(t), l'evolution et le pronostic de l'ARF chez ces malades, individuellement, etaient eclaircis.