Causes of Flank Pain (Acute)
| xxxxxxxxxxxxCommon โข Kidney Infection โข Kidney Stone โข Muscle Strain | xxxxxxxxxxLess Common โข Kidney Infarction โข Herpes Zoster (Shingles) โข Aortic Aneurysm (ruptured) |
1. Most patients with Flank Pain have a simple Muscle Strain
- Pain isnโt constant or severe
- Pain occurs especially with certain movements
- No Fever. No Nausea / Vomiting.
- Normal Urinalysis (โU/Aโ)
BUT โ Make sure patient doesnโt have a Kidney Infection or Kidney Stone
- Pain is persistent and moderate-to-severe
- Nausea or Vomiting
2. Symptoms help distinguish Kidney Infection from Kidney Stone:
- Kidney Stone usually begins abruptly (when stone gets stuck), Infection less so.
- Fever points to Infection, unless symptoms have continued long enough for a stone to become infected.
- No Fever strongly suggests a Stone (bladder infections donโt cause fevers, but kidney infections do).
- Urinary Symptoms like painful urination, or urge to urinate small amounts frequently, suggest an Infection that began in the bladder & went up to the kidney.
- Wave-like pain coming in episodes, lasting around 20 minutes, point to a Stone.
- Also think Stone for pain that radiates to groin, testicle, or labia.
- Infection almost always causes flank or back tenderness; Stones are non-tender when palpating the flank or pounding gently at mid-back..
- Recurrent episodes suggest Kidney Stones.ย Both Stone & Infection may cause nausea or vomiting.
- NOTE: There are many exceptions to the above, since symptoms of both Infection and Stone can be quite variable (even asymptomatic!)
3.ย Urinalysis (โUAโ) gives key information [clink for detailed discussion of the UA]
- No White Blood Cells (WBCs) = Definitely No Infection
- No Red Blood Cells (RBCs) = probably Not a Stone
- Positive WBCs / RBCs could be either
- High pH (>7.0) suggests Infection with the germs Klebsiella or Proteus, the latter of which can cause enormous permanent Stones.
4. Think about other rare but possibly catastrophic possibilities:
4a. Kidney Infarction (loss of blood supply kills some tissue)
- Suspect in patients with Atrial Fibrillation, metal Artificial Heart Valves, or rare clotting disorders sometimes found in Lupus & other diseases
- If such a patient has RBCs in UA, or unusually high blood pressure, send to ER
4b. Aortic Aneurysm (ruptured)
- Suspect in patients >60 yrs. old with long smoking history, or older patients whoโve had heart disease, stroke, or high blood pressure; AND WHO ALSO HAVE:
- Pain, that was never before felt, & began very abruptly!!!
- Send such patients to ER
5. Herpes Zoster (Shingles) [not catastrophic]
- Blisters or splotchy rash in a band-like area anywhere between spine & midline of abdomen
- Usually appear after 1-2 days of pain [making earlier diagnosis virtually impossible)
See Acute Flank Pain โ Full Text for more in-depth explanations and discussions.