We often say that we have “kidney pain” when the lower back pulls. Except that the kidneys don’t hurt all the time, and the lower back complains very often. Between simple lower back pain and real kidney pain, the clues are not the same.
The subject is all the more tricky as the two areas are close and the sensations merge when the pain surprises. Where it pinches, how it starts, what signs accompany it: these are the details that can guide the diagnosis.
Where it hurts: back pain or kidney pain
As a preamble, it is important to say that a kidney only hurts in cases of acute problem. Contrary to what one might believe, chronic kidney failure (especially when linked to hypertension or diabetes) does not cause any pain in the kidneys. In terms of location, kidney pain is more likely to be on one side, at the level of the flank under the last ribs, and can radiate towards the abdomen or groin. It is not centered on the column.
Conversely, the majority of lower back pain is caused by low back painoften mechanical, linked to muscles, ligaments or lumbar joints. Low back pain is felt in the lumbar region, sometimes with radiation towards the buttock or leg in the event of sciatica or cruralgia, common during a herniated disc.
Clearly, pain in the flank with radiation towards the groin is more reminiscent of the kidneys. If the symptom concerns the lumbar midline and the pain goes down the leg, then you should think about the back instead.
The type of pain and signs that point to the kidneys
On the kidney side, the
renal colic gives a sudden, very intense, often unbearable pain, which comes and goes in waves. There
pyelonephritiskidney infection, instead causes continuous pain with fever, chills and sometimes nausea. Back pain most often remains mechanical, variable, triggered by a false movement or bad posture, and worsens with everyday actions. Another useful difference: home remedies (rest, heat, simple analgesics) readily relieve lower back pain, whereas kidney pain do not give in with these means.
What to do in practice: low back pain or kidney pain, examinations and emergencies
You think of kidney pain, with fever, chills, burning when urinating, frequent urge to urinate, cloudy or smelly urine, or visible blood in the urine: consult quickly. In case of renal colic, nonsteroidal anti-inflammatory drugs (NSAIDs) can relieve pain, but they do not exempt you from consulting to confirm the diagnosis and treat the cause.
In case of pyelonephritis, antibiotic therapy is required. The assessment guides the rest: ECBU to check for infection, blood test for kidney function and inflammation, imaging if necessary (renal ultrasoundeven
scanner) to identify a kidney stone or enlargement.
If everything suggests common low back pain, the situation is most often benign. Strict rest is not recommended: resuming gentle and gradual activity helps you recover. Heat, appropriate stretching, massages, simple analgesics or muscle relaxants promote improvement. However, watch for warning signs that require rapid consultation: fever, unexplained weight loss, persistent pain at rest and at night, loss of strength in the leg, difficulty walking, numbness of the perineum, urinary or fecal problems that may suggest a
cauda equina syndrome.
And if you have already had stones or urinary infections, or an area at risk, do not delay in seeking advice, especially if the pain remains intense or returns in bouts.
• Back pain pure is often mechanical, linked to effort or poor posture, and calms down with rest or with anti-inflammatories;
• Kidney pain is deeper, sometimes constant, is often accompanied by fever, urinary symptoms (change in color or odor of urine, burning), and requires rapid medical consultation;
• Red flags for urgent consultation: high fever, intense unilateral pain, blood in the urine, urinary problems, malaise, or pain that persists despite rest or wakes you up at night.