최종 업데이트: 2026년 8월 27일

A kidney infection is a bladder infection that has climbed. It is far more serious than the cystitis it usually starts as, and it is one of the conditions in urology where the difference between a good outcome and a disaster is measured in hours.

If you have fever with flank pain

Get seen today. Not with a leftover antibiotic from a previous episode, and not by waiting to see whether it settles overnight. In an emergency in Thailand, call 1669. Go to hospital immediately rather than to a clinic if any of the following are present:

The distinction that matters most: is the kidney also blocked?

This was absent from the earlier version of this article entirely, and it is the most important thing a urologist has to say about kidney infection.

Most kidney infections settle with antibiotics. An infected kidney that is also obstructed — by a stone, a narrowing or a tumour — does not. Antibiotics travel in the bloodstream and cannot sterilise infected urine trapped behind a blockage; the pressure keeps rising, bacteria enter the bloodstream, and a patient can deteriorate from unwell to critically ill within hours.

That situation is a surgical emergency, and the treatment is drainage — a stent passed up to the kidney, or a tube through the skin — done urgently, with the stone or the underlying cause dealt with later once the infection has settled. It is not something antibiotics can be given time to work on.

Which is why the practical rule is: fever with flank pain in someone known to have stones, or who is not improving on antibiotics, needs a scan rather than a stronger prescription. 또한 참조하세요 narrowing of the ureter, which produces the same problem without a stone.

Escherichia coli, the organism responsible for most kidney infections
Most kidney infections are caused by bowel bacteria that have climbed the urinary tract.

How it happens

대장균, a normal inhabitant of the bowel, is responsible for most cases. It reaches the kidney in one of two ways:

  1. Climbing up from the bladder — by far the commoner route. The bacteria carry fine hair-like projections that let them grip the lining and work upwards from the urethra through the bladder and ureter.
  2. Through the bloodstream — uncommon, and mainly in people whose immunity is impaired.

It is several times commoner in women, whose urethra is short, with young sexually active women, infants, older people and pregnant women most affected.

Two groups where it is never just a kidney infection

증상

It develops fast, typically over hours. In older people the picture can be quieter and more confusing — confusion, unsteadiness or simply being unwell, sometimes without much fever — which is one reason kidney infection is missed in that group. Tapping over the kidney reproduces the pain, which is a useful bedside sign.

High fever with shaking chills, characteristic of acute kidney infection
Fever with one-sided flank pain is the combination to act on.

Tests and treatment

Urine testing shows inflammatory cells and bacteria, and a urine culture is taken before antibiotics are started — this is not a formality. It takes around two days and it is what allows a broad antibiotic to be narrowed to the right one, and what identifies a resistant organism if the first choice fails. Blood tests and blood cultures are added where the illness is more severe.

The earlier version described imaging as optional and reserved for severe cases. That is broadly right and worth stating more precisely, because it is how obstruction gets found. A scan is indicated where there are known stones, where the patient is a man, where there is diabetes or a single kidney, where the illness is severe — and, most importantly, where fever has not settled after about two to three days of appropriate antibiotics. A patient who is not improving is assumed to have something that needs draining until a scan says otherwise.

Antibiotics are started immediately after the culture is taken, by mouth for milder illness at home, intravenously in hospital for anyone vomiting, unstable, pregnant, or not improving. Finish the full course even once you feel well within a couple of days, and do not treat this with antibiotics bought over the counter — a partial course quietens the symptoms while leaving infection in the kidney and selecting for resistance.

What can go wrong

With prompt treatment the outlook is good. Delay, or an unrecognised blockage, allows an abscess in or around the kidney, bacteria in the bloodstream with septic shock, permanent scarring of the kidney, and — in people with diabetes especially — a rare gas-forming infection that destroys the kidney and is life-threatening. Diabetes is the single risk factor that turns a manageable infection into a dangerous one, which is why it lowers the threshold for admission and for scanning.

Drinking water, a preventive measure against recurrent urinary tract infection
Fluid intake is a preventive measure between episodes — not a treatment during one.

Preventing it happening again

Frequently Asked Questions About Kidney Infection

What are the symptoms?

Fever, often high and sudden with shaking chills; one-sided flank pain over the kidney; and nausea or vomiting. Burning and frequency are often present too. It develops over hours. In older people it can present as confusion or simply being unwell without much fever.

Why would antibiotics not be enough?

Because antibiotics cannot sterilise infected urine trapped behind a blockage. An infected kidney that is also obstructed by a stone or a narrowing is a surgical emergency needing urgent drainage, and a patient can deteriorate within hours. This is why failure to improve within two to three days prompts a scan rather than a stronger prescription.

Can I treat it at home?

Milder cases are treated at home with tablets after assessment and a urine culture. What is not safe is self-treating with leftover or over-the-counter antibiotics, which quietens symptoms while leaving infection in the kidney. Vomiting, instability, pregnancy, diabetes, a single kidney, known stones or failure to improve all point to hospital.

I am a man and I have had a kidney infection. Does that matter?

Yes. It is uncommon in men, so it is treated as a reason to look for an underlying cause — a stone, obstruction from the prostate, or an abnormality of the urinary tract. Treating the infection alone leaves the reason it happened unaddressed.

How do I stop it coming back?

Keep fluid intake up so urine stays pale, do not hold urine, wipe front to back, pass urine after sex — and have recurrent episodes investigated rather than repeatedly treated, since repetition usually means something is being missed.

진료 상담 예약 안내

An acute episode goes to hospital, not to an appointment. Afterwards, or for recurrent infections, Dr. Soarawee Weerasopone sees patients at Bangkok Hospital Headquarters 그리고 촌부리의 Samitivej Sriracha Hospital에서 진료하는 요일: 088-022-1445. Bring previous urine culture results and details of any antibiotics already taken — those two things shorten the process considerably.

방콕 병원 텔레메디시는 비긴급 상담을 위한 서비스로, 국제 환자도 이용 가능합니다. 이 경우 이메일로 이비인후과 부서에 사전에 예약하시기 바랍니다. bhquro@bdms.co.th. Samitivej Sriracha는 대면 진료만 가능합니다. 비용에 관한 문의는 이 웹사이트가 아닌 병원에서 답변해 드립니다.

면책 조항: 이 콘텐츠는 Bangkok Hospital Headquarters의 비뇨의학과 전문의인 Dr. Soarawee Weerasopone이 작성하고 감수한 것으로, 교육 목적으로만 제공됩니다. 개인에 대한 의학적 조언, 진단 또는 처방이 아니며, 개인 메시지 채널이나 소셜 미디어를 통해서는 어떠한 조언, 진단 또는 처방도 제공되지 않습니다. Dr. Soarawee는 공개 소셜 미디어 계정을 운영하지 않으며, 그의 이름으로 개인 상담을 제안하는 모든 계정은 사기입니다. 태국에서 응급 상황이 발생하면 다음 번호로 전화하십시오: 1669.

의학적 작성 및 검토: 소아라위 웨라소폰 박사(Dr. Pom) — 방콕 병원 본점 공인 비뇨기과 전문의, 2016년부터 비뇨기과 진료 중. 수련: 대만 창 Gung 기념병원 로봇 수술(2019) · 연수: 도쿄 준텐도 대학 병원 내비뇨기과(2022) · 연구원 및 임상 참관인, 미국 베이로 의과대학 스콧 비뇨기과(2025–2026).

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