Pathophysiology of Acute Renal Failure

Pathophysiology of Acute Renal Failure refers to acute decline in renal function in a short time together with a series of clinical symptoms like fluid and electrolytes disturbance, renal endocrine disorder, metabolic wastes accumulation in body and so on.

Types of Acute Renal Failure

1.Prerenal Acute Renal Failure

For some reasons, the effective circulatory blood volume declines and the renal blood vessels contract, which can cause the renal blood volume decreases dramatically. As a result, the glomerular filtration rate (GFR) declines.

2.Intrarenal Acute Renal Failure

Due to acute tubular necrosis, glomerular disease or interstitial diseases, they can cause renal parenchymal damage. Afterwards, the glomerular filtration rate (GFR) decreases.

3.Postrenal Acute Renal Failure

Kidney stone, tumor or adhesion, they can cause the urinary tract obstruction leading to decline in glomerular filtration rate (GFR).

Pathology of Acute Renal Failure

1. Glomerular filtration rate( GFR)

*Renal blood volume decreases

*The glomerular effective filtration pressure declines

*The permeability of glomerular membrane and effective filtration area reduce.

2. Tubular obstruction

Nephrotoxicant and/ or hemolysis can cause cast urine leading to tubular obstruction. Moreover, some medicines crystals can deposit in renal tubular lumen, which is also a reason for tubular obstruction.

3. Reflux of urine

Renal poisoning and persistent renal ischemia can cause acute renal tubular necrosis. As a result, the primary urine flows reversely into renal interstitium thus leading to edema of renal interstitium.

Functional and metabolic alternations

First, oliguric Acute Renal Failure

1. Oliguric phase

(1) Alteration of urine

The urine volume is less than 400 ml/d and the patients even may experience anuria.

(2) Azotemia

For the GFR declines, the metabolic products nitrogen stimulate in body. As a result, the non protein nitrogen level increases in blood leading to azotemia.

(3) Water intoxication

For oliguria and even anuria as well as metabolic disorders, it can cause more water to build up in body leading to water intoxication.

(4) Hyperkalemia

With the decline in renal function, less potassium is discharged from body. Moreover, the metabolic disorders can cause the potassium to release. Also the acidosis can make the intracellular potassium transfer to outside of the cells.

2. Diuretic phase

The urine output is above 400 ml/d. The renal blood volume and the glomerular filtration rate (GFR) recovers normal as well as the renal tubular obstruction disappear. However, the renal concentration ability still does not recover. Moreover, the kidneys excrete the excess water from body for their compensatory capacity. Therefore, the patients with Acute Renal Failure experience diuretic phase.

3. Recovery phase

Second, nonoliguric Acute Renal Failure

(1) The patients with nonliguric Acute Renal Failure do not have obvious decline in urine output volume.

(2) Specific gravity is low.

(3) Urine sodium level is low

(4) Azotemia

(5) Most of the patients do not have hyperkalemia.

Once you are diagnosed with Acute Renal Failure, you should receive treatment at once to avoid further damage to kidneys. If you want to know more about the disease, please consult us on line.

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