Differential Diagnosis
- Single most likely diagnosis
- Low back pain due to pregnancy-related mechanical changes: The patient's symptoms of dull, low back pain radiating to the buttocks and posterior thighs, worsening with activity and improving with rest, are consistent with mechanical low back pain. The wide, waddling gait and absence of spinal or paravertebral tenderness also support this diagnosis. The patient's significant weight gain during pregnancy and the fact that she is at 32 weeks gestation, a time when the fetus is large enough to cause significant mechanical stress on the back, further justify this diagnosis.
- Other Likely diagnoses
- Lumbar disc herniation: Although less likely than mechanical low back pain, the patient's history of post–lumbar puncture headache and epidural blood patch after her first pregnancy raises the possibility of a lumbar disc herniation, especially given her current symptoms of low back pain radiating to the buttocks and posterior thighs.
- Symphysis pubis dysfunction: The patient's wide, waddling gait and complaint of low back pain could also be consistent with symphysis pubis dysfunction, a condition characterized by inflammation of the symphysis pubis joint.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Pre-eclampsia: Although the patient's blood pressure is currently normal, the presence of ankle edema and urinary frequency could be indicative of pre-eclampsia, a condition that can be deadly if left untreated.
- Spinal epidural hematoma or abscess: Given the patient's history of epidural anesthesia and blood patch, there is a small risk of spinal epidural hematoma or abscess, which would require immediate medical attention.
- Rare diagnoses
- Osteoporotic compression fracture: Although rare in a 36-year-old woman, osteoporotic compression fracture could be a consideration, especially if the patient has a history of osteoporosis or is taking medications that increase the risk of osteoporosis.
- Neoplastic processes: Neoplastic processes, such as multiple myeloma or metastatic cancer, are rare but could present with low back pain and should be considered if other diagnoses are ruled out and the patient's symptoms persist or worsen.