Differential Diagnosis for 3rd Trimester Pregnancy Flank Pain

Single Most Likely Diagnosis

• Pyelonephritis: This condition is a common cause of flank pain in pregnancy, especially in the 3rd trimester. The presence of mild leukocyte esterase in the urine analysis supports this diagnosis, as it indicates a possible urinary tract infection. Pyelonephritis can lead to significant morbidity if not treated promptly.

Other Likely Diagnoses

• Nephrolithiasis (Kidney Stones): Although less common in pregnancy due to increased urine pH and citrate levels, kidney stones can still occur and cause flank pain. The presence of ketones might suggest dehydration, which could contribute to stone formation.
• Urinary Tract Infection (UTI) without Pyelonephritis: A lower urinary tract infection could also present with leukocyte esterase and cause discomfort that might be perceived as flank pain, especially if the infection is severe or involves the upper urinary tract.
• Preeclampsia: While primarily associated with hypertension and proteinuria, preeclampsia can sometimes present with abdominal or flank pain due to liver capsule distension (Hellp syndrome) or other complications.

Do Not Miss Diagnoses

• Placental Abruption: Although not directly related to the urine analysis findings, placental abruption can cause severe abdominal or back pain and is a life-threatening condition for both the mother and the fetus. It's crucial to consider this diagnosis in any pregnant patient presenting with abdominal or flank pain.
• Appendicitis: Appendicitis can present with atypical pain in pregnancy, sometimes perceived as flank pain, especially if the appendix is retrocecal. Missing this diagnosis can lead to severe consequences, including perforation and peritonitis.
• Renal Infarction: A rare but potentially life-threatening condition that could present with acute flank pain. It might not be directly suggested by the urine analysis but should be considered in the differential due to its severity.

Rare Diagnoses

• Renal Cell Carcinoma: Although rare, renal cell carcinoma can cause flank pain and might be associated with hematuria or other abnormalities in the urine analysis, though not directly indicated here.
• Hydronephrosis due to Ureteral Obstruction: Pregnancy can cause ureteral obstruction due to the gravid uterus, leading to hydronephrosis. This condition might present with flank pain and could potentially show abnormalities in the urine analysis, including proteinuria due to renal damage.