What causes decreased urine output?

For the human body, urination is a normal physiological phenomenon. The main purpose of urination is to expel excess waste water from the body to ensure normal metabolism. However, many people experience decreased urine output due to various reasons. Generally speaking, decreased urine volume can be divided into prerenal oligouria, renal oligouria and postrenal oligouria. Different symptoms have different causes. Below we will introduce in detail the reasons for low urine volume.

1. Prerenal low urine volume

Insufficient renal perfusion due to various reasons and a sharp drop in glomerular filtration rate are called prerenal oligouria and anuria.

(1) Insufficient blood volume: It starts with functional oliguria and anuria. Once the blood volume is replenished, the urine volume will recover immediately. If it is not diagnosed and treated in time, it may cause organic kidney damage and acute renal failure, manifested as low urine volume or anuria, which is seen in severe dehydration, massive bleeding, large-area burns, etc.

(2) Shock: Shock due to various reasons causes a decrease in renal perfusion pressure and a serious deficiency in glomerular filtration rate. It is seen in anaphylactic shock, hemorrhagic shock, cardiogenic shock, infectious and toxic shock, etc.

(3) Decreased cardiac output: At this time, the blood supply to the kidneys decreases significantly, which is seen in left heart failure, severe arrhythmias, cardiac tamponade and constrictive pericarditis.

(4) Hepatorenal syndrome: In the late stage of cirrhosis, there is severe ascites and severe renal hypoperfusion, which manifests as low urine volume or anuria. Once the ascites of cirrhosis is relieved, the kidneys will recover and the urine volume will increase.

2. Renal low urine output

(1) Renal parenchymal damage: Whether it is primary glomerulonephritis or secondary to systemic lupus erythematosus, polyarteritis nodosa, infective endocarditis, dermatomyositis, etc., it can cause renal parenchymal damage and even renal function damage or failure, resulting in low urine output.

(2) Renal interstitial disease: The most common drug allergies such as penicillin, sulfonamides, rifampicin, aminoglycoside antibiotics, etc. cause renal interstitial damage.

(3) Renal vascular diseases: renal cortical vasospasm or embolism, reduced renal blood supply causing oliguria, seen in disseminated intravascular coagulation, large area burns, etc.

3. Postrenal low urine output

It is common in urinary tract obstruction such as stones, tumors, prostate hypertrophy or prostate cancer.