Differential Diagnosis for Flank Pain at 32 Weeks Pregnancy

• Single most likely diagnosis
  • Pyelonephritis: This is a common condition in pregnancy, especially in the second and third trimesters, due to urinary stasis and ureteral dilation. The symptoms of flank pain, fever, and urinary frequency make it a likely diagnosis.
• Other Likely diagnoses
  • Nephrolithiasis (Kidney Stones): Although less common in pregnancy, kidney stones can cause severe flank pain and may be associated with nausea, vomiting, and hematuria.
  • Urinary Tract Infection (UTI): Similar to pyelonephritis but limited to the lower urinary tract, UTIs are common in pregnancy and can cause flank pain, dysuria, and frequent urination.
  • Musculoskeletal strain: The growing uterus can put strain on the back and abdominal muscles, leading to flank pain.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Placental abruption: Although more commonly associated with vaginal bleeding and abdominal pain, placental abruption can sometimes present with flank pain and is a medical emergency.
  • Pulmonary embolism: While less common, pulmonary embolism is a significant risk in pregnancy due to hypercoagulability and can present with sudden onset of flank or chest pain and shortness of breath.
  • Ruptured ovarian cyst: Although rare, a ruptured ovarian cyst can cause severe flank pain and is a surgical emergency.
• Rare diagnoses
  • Renal vein thrombosis: This is a rare condition that can occur in pregnancy, especially in the setting of nephrotic syndrome or dehydration, and presents with flank pain and hematuria.
  • Ureteral obstruction: This can be due to various causes, including stones, blood clots, or external compression, and is a rare but serious condition requiring prompt intervention.