Loin Pain

Doctors may disagree – with patients and among themselves – about where exactly the ‘loin’ is. For the purposes of this chapter, it is the area between the lower ribs and the pelvis, anteriorly or posteriorly. Loin pain is a common acute or subacute presentation, with patients tending to assume that the symptom inevitably represents a renal problem. Occasionally, they are correct. But a musculoskeletal aetiology is much more likely, and there are other possible causes to trip up the unwary.

Published: 1st August 2022 | Updated: 15th August 2022

Differential diagnosis

Common Diagnoses

  • Acute Musculoskeletal Pain
  • Renal or Ureteric Stone
  • Acute Pyelonephritis
  • Rib Pain
  • Shingles

Occasional Diagnoses

  • Gynaecological Causes (e.g. Ectopic Pregnancy, PID, Ruptured or Torted Ovarian Cyst)
  • Gastrointestinal Causes (e.g. Appendicitis, Biliary Colic)
  • Other Urological Causes in Men (e.g. Epididymitis, Prostatitis)
  • Pelvi-Ureteric Obstruction
  • Radicular Pain (e.g. from Osteoarthritis or Disc Prolapse)

Rare Diagnoses

  • Leaking Abdominal Aortic Aneurysm
  • Retroperitoneal Fibrosis
  • Renal Infarction
  • Renal Tumour (Either Directly or by Causing a Blood Clot in the Ureter)
  • Acute Papillary Necrosis
  • Factitious (e.g. Addicts Seeking Opioids)
  • Idiopathic Loin Pain Haematuria Syndrome

Ready reckoner

Key distinguishing features of the most common diagnoses

Acute Musculoskeletal PainRenal or Ureteric StoneAcute PyelonephritisRIB PainShingles
Urinary SymptomsNoPossiblePossibleNoNo
Macro or Microscopic HaematuriaNoPossiblePossibleNoNo
Pain w Worse with MovementYesNoNoPossibleNo
Pain ColickyNoYesNoNoNo

Possible investigations

Likely: Urinalysis, MSU.

Possible: U&E, sieving urine, renal imaging.

Small Print: Metabolic screen (usually secondary care); other hospital-based investigations.

  • Urinalysis: The presence of microscopic haematuria would support your diagnosis of renal/ ureteric colic (though its absence does not rule it out); urinalysis may also reveal evidence of urinary infection or acute papillary necrosis (blood and white cells in the latter).
  • MSU: To confirm suspected infection; also might suggest acute papillary necrosis (blood and sterile pyuria).
  • U&E: To assess renal function when underlying renal issue suspected.
  • Sieving urine: To retrieve stone in renal/ureteric colic for subsequent analysis.
  • Renal imaging: Non-contrast helical CT is the hospital investigation of choice in suspected renal/ureteric colic; depending on how acute the presentation is, and on local pathways and guidelines, plain abdominal X-ray or US may be helpful. Renal imaging may also be required in acute pyelonephritis (especially if recurrent), possible renal tumour and in suspected pelvi-ureteric obstruction. Ultrasound, IVU, CT or MRI may be needed to diagnose retroperitoneal fibrosis.
  • Metabolic screen such as blood and 24 hour urine for calcium, phosphate and urate in stone formers.
  • Other hospital-based investigations: Required to clarify the diagnosis in those admitted, and will depend on whether the cause seems urological, gynaecological or gastrointestinal.

Top Tips

  • Remember that many patients fear kidney problems. They may value reassurance that all is well renally as much as your positive diagnosis of musculoskeletal pain.
  • Take care during busy telephone triaging sessions – be sure to check that the apparently simple case of cystitis isn’t actually a developing case of acute pyelonephritis.
  • The absence of microscopic haematuria does not rule out renal/ureteric colic but should certainly prompt a consideration of alternative diagnoses.
  • Patients with genuine renal/ureteric colic tend to writhe about in pain.
  • Think of shingles, particularly in elderly patients with an otherwise unexplained short history of burning loin pain, and warn them of the possibility of a rash developing – the pain may precede the skin manifestations by a few days.

Red Flags

  • Beware of a first diagnosis of renal/ureteric colic (especially left sided) in older men – a leaking abdominal aortic aneurysm can cause very similar symptoms.
  • Some cases of renal/ureteric colic can be managed – at least initially – in the community. But those with fever, prolonged or unresponsive pain, or known renal compromise should be admitted.
  • Remember that acute pyelonephritis in men and children, and recurrent episodes in women, require investigation to exclude any underlying urological problem.
  • Be cautious about using strong analgesics for possible renal/ureteric colic in patients with past histories of drug addiction – this used to be a favoured way of engineering a free opioid fix, although the increasing use of diclofenac as the urgent treatment of choice has reduced this problem.
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Website disclaimer

Pulse Reference is based on the best-selling book Symptom Sorter.

The experts behind Pulse Reference are Dr Keith Hopcroft who is the co-author of Symptom Sorter, a GP in Essex and Pulse’s editorial advisor and Dr Poppy Freeman, a GP in Camden and also a clinical advisor to Pulse.

This website is for clinical guidance only and cannot give definitive diagnostic information. Practitioners should work within the limits of their individual professional practice, seek guidance when necessary and refer appropriately.