MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Ya.I. Fedonyuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

CHAPTER 8. THE PROCESS OF URINATION AND ITS PATHOLOGY

ANATOMY AND PHYSIOLOGY OF THE URINARY ORGANS

PATHOLOGY OF THE KIDNEYS AND URINARY BLADDER

FUNCTIONAL DISORDERS OF URINATION

KIDNEY DISEASES

2. TUBULOPATHIES

2.1. ACUTE RENAL FAILURE

Acute renal failure is a sudden, drastic impairment of all or nearly all renal Functions, underpinned by tubular epithelial necrosis (necronephrosis).

A hallmark manifestation of acute renal failure is, first and foremost, a sharp decrease in urine output (down to complete anuria), resulting in the accumulation of excessive amounts of nitrogenous waste products in the body, as well as fluid-electrolyte and acid-base balance disorders. In uncomplicated cases, these processes are reversible. Rational and timely Treatment is effective.

Any complication leads to severe functional and morphological alterations across all body systems, culminating in patient death.

Renal failure is triggered by prerenal, renal, and postrenal factors.

In the initial stage of acute renal failure, the organ's function suffers as a consequence of impaired Blood Circulation and metabolic processes within the Kidney. Subsequently, morphological changes develop, primarily within the nephron tubules. Frequently, these renal changes in individuals who have died from acute renal failure are entirely minimal or inconsistent with the clinical manifestations.

Macroscopically, the Kidneys are enlarged, soft, and flabby. The fibrous capsule strips away easily, the cortical substance is bloodless, and the renal pyramids are engorged with blood ("Shock Kidney").

Histological examination reveals flattening of the nephron tubular epithelium, infiltration and edema of the interstitial tissue, and areas of necrosis. These changes remain uniform regardless of the underlying cause of anuria.

Acute renal failure comprises four stages: a) initial or shock stage; b) oligoanuria stage (daily urine output drops below 300 mL); c) recovery of diuresis stage (daily urine output exceeds 300 mL); d) convalescence stage (normalization of blood nitrogen levels).

In acute renal failure, the majority of patients succumb during the peak of the oligoanuric stage. With a favorable clinical course, the stages of diuresis recovery and polyuria set in after 5–7 days. The increase in Glomerular Filtration is driven both by the restoration of this process in functioning nephrons (at the onset of polyuria) and the subsequent (months later) increase in the mass of functional nephrons. Other renal functions gradually recover as well.