Kidney infection
A kidney infection, or pyelonephritis, is an inflammation that began not in the bladder but higher up, in the kidney itself.
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Medicines commonly prescribed for Kidney infection
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: ORAL SOLUTION/SUSPENSION, 1000 mgActive substance: amoxicillinManufacturer: Laboratorios Normon S.A.Prescription requiredDosage form: TABLET, 500 mg/125 mgActive substance: amoxicillin and beta-lactamase inhibitorManufacturer: Almus Farmaceutica S.A.U.Prescription requiredDosage form: ORAL SOLUTION/SUSPENSION, 250 mgActive substance: amoxicillinManufacturer: Laboratorios Normon S.A.Prescription required
A kidney infection, or pyelonephritis, is an inflammation that began not in the bladder but higher up, in the kidney itself. What separates it from cystitis is not how much it stings to pass water, but the fact that the person feels genuinely ill: the temperature climbs, the small of the back aches, there are chills and nausea. It is treated with ordinary antibiotics and in most cases clears without a trace, but it is not something to sit on: the kidney has an extremely rich blood supply, and infection passes from it into the bloodstream quickly.
How the microbes reach the kidney
Almost always they travel upwards. Bowel bacteria, most often Escherichia coli, reach the opening of the urethra, climb into the bladder and from there pass up the ureter into the renal pelvis. Far less often microbes arrive through the blood from another focus, from an infection of the heart valves for instance.
Women get it many times more often: the urethra is short and sits close to the anus, so the journey for bacteria is a short one. In men kidney infection is less common, and there is nearly always something blocking the outflow behind it — an enlarged prostate, a narrowing, a stone. The odds rise wherever urine stagnates or flows backwards: with stones, an enlarged prostate, a catheter, in pregnancy, and in children whose urine refluxes from the bladder back up the ureter. Diabetes and anything that weakens immunity stand apart: in those people the infection runs a heavier course.
How to tell it is not cystitis
Cystitis means stinging, frequent urges and cloudy urine, but general wellbeing is barely affected. A kidney infection adds what cystitis does not have:
- a temperature above 38 °C, often with shivering so hard that no amount of blankets helps;
- pain in the loin or the flank, usually on one side, dull and constant;
- nausea, vomiting, sometimes diarrhoea;
- aching muscles and the feeling of coming down with flu;
- weakness heavy enough to make standing up an effort.
Burning on passing water, urgency, and dark or cloudy urine with a strong smell may be there as well, or may be absent altogether: a kidney infection often begins straight away with fever and pain in the side.
In small children it looks quite different. A child under two frequently has nothing but a high temperature; there may be vomiting, refusal of feeds, listlessness, unexplained irritability, and in babies poor weight gain and jaundice. An older child who has been dry for a long time and starts wetting the bed again is also a reason to look. Any fever in a young child without an obvious cause is grounds for a urine test rather than for waiting to see whether a cold appears. In older people there may be no fever at all, and the only sign is sudden confusion, a fall or abrupt weakness.
When waiting becomes dangerous
Call an ambulance — in Spain, Italy, Portugal, Poland and Ukraine the number is 112 — or take the person straight to hospital if there are signs that the infection has entered the blood:
- confusion, drowsiness, slurred speech, difficulty rousing the person;
- very fast, shallow breathing;
- skin that is pale, mottled, bluish, or cold and clammy;
- a rash that does not fade when pressed with a clear glass;
- no urine passed for many hours in a row;
- extreme muscle pain and a sense of impending death — patients describe this often, and it should not be put down to panic.
Being seen the same day, rather than tomorrow, is needed when fever and flank pain appear in pregnancy; when vomiting prevents drinking and keeping medicines down; in anyone with diabetes, on treatment that suppresses immunity, or living with a single kidney; and when the pain in the side comes in waves and is very severe, which is how a stone blocking the ureter behaves. One more signal on its own: no improvement after forty-eight hours of antibiotics.
What must not be missed
There is one situation in which antibiotics alone are not enough. If the ureter is blocked by a stone or a tumour, pus inside the kidney sits under pressure, the drug cannot reach it, and the person deteriorates despite treatment. Such a kidney has to be drained urgently, either by bringing urine out through a tube or by placing a stent inside. Suspicion comes from high fever together with severe colicky pain and no response to antibiotics; ultrasound or a CT scan confirms it. Delay here is the most dangerous thing in this whole subject.
In people with poorly controlled diabetes an unusually severe variant occasionally occurs, in which gas forms within the kidney tissue. That too calls for hospital rather than tablets.
Which tests are needed
The foundation is a urine test. A dipstick shows white cells and nitrites within a minute, but what really matters is a urine culture with sensitivities: it says which organism is responsible and which drug will deal with it. The sample for culture should be collected before the first tablet, otherwise the result comes out blurred. Blood is taken as well, for inflammatory markers and creatinine, and in severe illness for blood cultures.
Kidney ultrasound is not for everybody. It is called for when there is no improvement within two or three days, when infections keep coming back, when the patient is a man or a child, when a stone is suspected, or when there is visible blood in the urine. If the picture stays unclear, a CT scan takes the place of ultrasound.
How it is treated
The mainstay is an antibiotic by mouth, usually for one to two weeks. It is chosen blind at first, based on which organisms predominate locally, and changed once the culture comes back if that is needed. Improvement normally shows within a day or two; if it does not, the treatment needs reviewing rather than more patience.
The course has to be finished even when the person feels well again by the third day. Stopping early leaves some bacteria alive, and the infection returns in a more resistant form.
Admission for intravenous antibiotics follows when vomiting makes tablets impossible, in pregnancy, in severe illness, when a blocked ureter is suspected, and in people with serious underlying conditions. After a few days treatment usually switches back to tablets and finishes at home. Strength does not return at once: tiredness and being easily worn out last another couple of weeks, and that is normal.
What to do at home
- drink enough, in small sips if you feel sick; pale urine is the guide. If you have kidney or heart disease and your fluids are restricted, ask your doctor how much is allowed;
- rest, and do not try to go back to work the day after starting the antibiotic;
- take paracetamol to bring the temperature down and ease the pain; for a child, the children's preparation at the weight given on the leaflet;
- do not take ibuprofen, diclofenac or other anti-inflammatory painkillers unless a doctor has advised them: during a kidney infection they put extra strain on the kidney;
- do not hold on when you need to pass water, and try to empty the bladder fully;
- warmth on the back and herbal teas are no substitute for an antibiotic — they may ease the feeling, but they do nothing to the bacteria.
Keeping it from coming back
Drink water through the day, do not put off going to the toilet, pass urine after sex, wipe from front to back, and treat constipation, because a full rectum stops the bladder emptying. Perfumed intimate hygiene products and vaginal douching disturb the natural flora and help nothing.
When infections keep returning, the task changes: what needs finding is not another antibiotic but the reason. In women after the menopause, some of the recurrences relate to a lack of oestrogen in the lining, and local treatment discussed with a doctor helps there. In men a repeat infection nearly always means an obstruction to outflow and calls for investigation. A child with a confirmed kidney infection is checked for urine refluxing upwards: pyelonephritis that was undertreated in childhood leaves scars on the kidney, and years later those scars turn into high blood pressure and chronic kidney disease.
Online consultation
In an online consultation the doctor will work out whether your symptoms point to a kidney infection or to cystitis, and explain which tests to have first and how to collect a urine sample for culture properly. They will help you read results you already have, check for the signs that make hospital necessary, and tell you what to do if there is no improvement by the second day of treatment. Recurring infections can be discussed too: the doctor will suggest which investigation is worth doing to find the cause, rather than treating each episode from scratch.
This material is for information only and does not replace medical advice.
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