Acute Flank Pain

Causes of Flank Pain (Acute)

xxxxxxxxxxxxCommon  
โ€ข Kidney Infection
โ€ข Kidney Stone
โ€ข Muscle Strain  
xxxxxxxxxxLess Common  
โ€ข Kidney Infarction
โ€ข Herpes Zoster (Shingles)
โ€ข Aortic Aneurysm (ruptured)

1.  Most patients with Flank Pain have a simple Muscle Strain

  • Pain isnโ€™t constant or severe
  • Pain occurs especially with certain movements
  • No Fever.  No Nausea / Vomiting.
  • Normal Urinalysis (โ€œU/Aโ€)

BUT โ€“ Make sure patient doesnโ€™t 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 donโ€™t 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 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.  Urinalysis (โ€œU/Aโ€) gives key information [clink for detailed discussion of the U/A]

  • 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 U/A, 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 whoโ€™ve 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.

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