Pyelonephritis: Symptoms, Causes & Treatment

Acute kidney infection, medically known as pyelonephritis, is a bacterial infection affecting the kidney itself and its urine-collecting system. In most cases the infection begins in the bladder (lower urinary tract infection) then ascends through the ureter to the kidney, so kidney infection is much more dangerous than a simple bladder infection, because it affects a vital organ and may lead to serious complications if not treated quickly.

The symptoms of acute pyelonephritis are more severe than those of a bladder infection, and include: high fever and chills, pain in the flank or back on the side of the affected kidney (a characteristic sign), nausea and vomiting, a general feeling of tiredness and exhaustion, in addition to urinary symptoms such as burning on urination, frequency, and urgency, and sometimes cloudy, foul-smelling, or bloody urine. Kidney infection is more common in women due to their shorter urethra, and its likelihood increases with pregnancy, urinary tract stones, diabetes, weak immunity, and any obstacle preventing normal urine flow.

Acute kidney infection is a condition requiring prompt diagnosis and treatment, as it is diagnosed by symptoms, a urine test and culture (to identify the bacteria and the suitable antibiotic), and sometimes blood tests and imaging. The main treatment is antibiotics, which may be given orally in mild to moderate cases with close monitoring, while severe cases or those with vomiting preventing taking the medication, signs of blood poisoning, or an obstruction need hospital admission and intravenous antibiotics and fluids. It is important to complete the full antibiotic course and drink plenty of fluids. If kidney infection is left untreated it may lead to serious complications such as blood poisoning, a kidney abscess, or impaired kidney function. Therefore, any high fever with flank pain and urinary symptoms requires urgent medical review without delay.

• High fever and chills.
• Pain in the flank or back on the side of the kidney (a characteristic sign).
• Nausea, vomiting, and general fatigue.
• Burning, frequency, and urgency in urination, and cloudy or bloody urine sometimes.

• A bacterial infection usually ascending from the bladder to the kidney.
• More common in women (shorter urethra).
• Factors: pregnancy, urinary stones, diabetes, weak immunity, and any obstruction to urine flow.

• Symptoms, a urine test, and culture (to identify the bacteria and suitable antibiotic).
• Blood tests when needed.
• Imaging when an obstruction, stone, or abscess is suspected.

Mild to moderate cases

• Oral antibiotics with close monitoring and drinking fluids.

Severe cases

• Hospital admission and intravenous antibiotics and fluids (with vomiting, blood poisoning, or obstruction).

It is important to complete the full antibiotic course. This content is educational and does not replace urgent medical care.

• Blood poisoning (a serious condition).
• Formation of a kidney abscess.
• Impaired kidney function with delayed treatment or recurrence.

• Treating bladder infections early before they ascend to the kidney.
• Drinking plenty of water, urinating when needed, and not holding it.
• Controlling diabetes and treating urinary stones and any obstruction.