Anuria is a condition when a person is unable to pass urine or passes an insignificant amount of urine which is less than 100 milliliters in 24 hrs. This may be due to an underlying cause like:

Low blood pressure due to excessive blood loss, severe diarrhea/vomiting, severe infection

End-stage renal disorder

Obstruction to urinary tract due to kidney tumors or kidney stones

The main role of kidneys is the excretion of waste substances from the body in the form of urine. Kidneys also help in regulating blood pressure, salt and electrolyte balance, and acid-base balance in the body. The daily urine output is around 800 to 2,000 milliliters per day. In the case of anuria, toxic waste substances get accumulated in the body leading to severe manifestations.

Causes of Anuria:

Low Blood Pressure: This may be due to excessive blood loss, severe dehydration due to vomiting or diarrhea, or severe infection which decreases blood supply to kidneys leading to acute kidney injury and anuria.
Diabetes: Unmanaged diabetes can cause diabetic ketoacidosis. This is one of the causes of acute kidney failure that may lead to anuria.
Advanced Kidney failure or End-stage kidney disease: During this stage, the kidney has lost almost all functions and is unable to excrete any urine. Kidney stones are stone-like hard deposits of minerals that are formed due to concentrated urine which crystalizes the minerals into stone form. These stones when big enough may block the entire urine output.
Tumors of kidneys: Tumors hamper kidney function and block the urinary tract at different levels and can cause decreased urine output.

Symptoms:

Swollen foot and ankle: This symptom may sometime appear due to fluid retention in patients with kidney disease and reduced urine output.
Distress, pain, or difficulty initiating urination.
Hematuria or blood in urine: This happens commonly in either glomerular diseases or patients with kidney stones or tumors.
Generalized weakness, decreased appetite, and repeated vomitings.

Diagnosis:

Urine tests

Blood tests for elevated waste product levels in the blood such as blood Urea/Creatinine
Ultrasound to assess kidney, ureters, bladder, and prostate (in males)

CT scan / MRI as per clinical suspicion

Renal scintigraphy may be required in some cases to assess kidney function via nuclear medicine
Kidney biopsy using a trivial sample of kidney tissue if required

Treatment:

Treating underlying cause:

Dehydration or Hypotension may be corrected with intravenous fluids and treatment of any underlying infections in patients with acute kidney injury
Kidney stone treatment will depend on the size and location of the stone
Dialysis as supportive therapy is required in patients having severe manifestations
Ureteral stents for patients with ureteric obstruction
Surgical tumor removal and management through chemotherapy and radiation therapy as recommended
Kidney transplant in patients with End-stage renal disease

Take all your contemporary medications on time (Diabetes, Hypertension, Thyroid)

Lifestyle changes

Limit foods high in sugar and fat
Fruit and vegetable servings as per dietician advice
Include low-fat products
A low-salt and low-fat diet, avoid any special salts like TATA Lite/Lona/Sendha namak
Fluid intake as advised by the doctor
Regular physical activity for at least 30-45 min a day, could be walking, cycling and lightweights
Manage stress by meditation, pranayama, and yoga

While you have known all about anuria, I would like to share another important fact. Earlier in the detection of underlying cause better is the outcome. Stay aware, keep healthy!