A 36-year-old woman comes to the physician because of abdominal pain for the last two days, which she attributes to a urinary infection. She had one episode of vomiting in the morning and she also complains of sweating and restlessness. She states that she sometimes experiences these attacks after 'her urine turns dark.' Previous trips to the emergency department for abdominal pain were treated with pain killers. A previous CT scan was normal during a past episode of abdominal pain. Two years ago, she was treated for Trichomonas vaginalis infection. She has chronic constipation and takes over-the-counter laxatives.
Her past medical history is otherwise unremarkable. She is sexually active with one partner, and she has been taking oral contraceptive agents on and off over the last several years. She is trying to lose weight by following a low-calorie, low-carbohydrate diet.
Her temperature is 36.7 C (98 F) , blood pressure is 165/97 mm Hg, and pulse is 112/min and regular. Her BMI is 29 kg/m². Her abdomen is soft with mild diffuse tenderness and no rebound tenderness or rigidity. There is no costovertebral angle tenderness. Bimanual pelvic examination is unremarkable. Laboratory results are as follows:

Urine pregnancy test is negative. Abdominal flat plain film is unremarkable.
Which of the following is the most likely diagnosis?

Question

A 36-year-old woman comes to the physician because of abdominal pain for the last two days, which she attributes to a urinary infection. She had one episode of vomiting in the morning and she also complains of sweating and restlessness. She states that she sometimes experiences these attacks after 'her urine turns dark.' Previous trips to the emergency department for abdominal pain were treated with pain killers. A previous CT scan was normal during a past episode of abdominal pain. Two years ago, she was treated for Trichomonas vaginalis infection. She has chronic constipation and takes over-the-counter laxatives.
Her past medical history is otherwise unremarkable. She is sexually active with one partner, and she has been taking oral contraceptive agents on and off over the last several years. She is trying to lose weight by following a low-calorie, low-carbohydrate diet.
Her temperature is 36.7 C (98 F) , blood pressure is 165/97 mm Hg, and pulse is 112/min and regular. Her BMI is 29 kg/m². Her abdomen is soft with mild diffuse tenderness and no rebound tenderness or rigidity. There is no costovertebral angle tenderness. Bimanual pelvic examination is unremarkable. Laboratory results are as follows:

Urine pregnancy test is negative. Abdominal flat plain film is unremarkable.
Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec193a_9822_6086_853d_e1cdb4cf6dc2_MD0002_00 This patient has recurrent abdominal pain, constipation, dark urine, and hyponatremia suggesting possible acute intermittent porphyria (AIP). Acute intermittent porphyria is caused by elevated porphobilinogen (PBG) and alpha aminolevulinic acid in tissues due to a heme pathway enzyme deficiency (hepatic PBG deaminase). Factors precipitating AIP include starvation, stress, infection, alcohol intake, drugs (most commonly hormones and sulfonamides), and low carbohydrate intake (as in this patient). Patients present most commonly with recurrent episodes of severe abdominal pain, often associated with constipation and signs of ileus (i.e., nausea, abdominal distention, and decreased bowel sounds) due to autonomic neuropathy. Bladder dysfunction resulting in urinary retention, incontinence, or dysuria can be confused with urinary tract infection. Dark or reddish urine is an important clue. Sensory neuropathy can occur early, but motor neuropathy (painful flaccid paralysis) is usually a late manifestation. Hyponatremia is attributed to inappropriate secretion of antidiuretic hormone and increases the risk for seizure. Tachycardia and hypertension due to catecholamine release during the attack (from pain) are common. reddish urine Elevated urinary porphobilinogen measurement confirms the diagnosis, but is best measured during an acute attack. Treatment includes symptomatic therapy, glucose loading, and intravenous hemin (reconstitutes the regulatory heme pool in the liver to lower PBG). Future attacks can be prevented by avoiding precipitating factors. (Choice B) Opioid-seeking behavior is the most common misdiagnosis in patients with porphyria, and should be a diagnosis of exclusion. (Choice C) Pelvic inflammatory disease (PID) is the most common cause of recurrent abdominal pain in young women. PID presents with vaginal discharge and tenderness (e.g., uterine, adnexal, or cervical motion) on a bimanual examination. It is less likely in this patient with a normal bimanual exam. (Choice D) Pheochromocytoma can cause symptoms and signs of sympathetic hyperactivity, but does not cause dark urine and abdominal pain. (Choice E) Struvite kidney stones are more common in women > age 50 and usually present with recurrent UTI, hematuria, and flank pain. These stones tend to form large staghorn calculi, which are usually radiopaque. This patient's normal abdominal x-ray and previously normal CT scan make this diagnosis unlikely. Educational objective: Patients presenting with recurrent acute abdominal pain combined with dark urine and hyponatremia should be evaluated for acute intermittent porphyria. The diagnostic test is an elevated urinary porphobilinogen (PBG) during an acute attack. Treatment involves glucose loading and intravenous hemin. __________ References: Intensive care management of patients with acute intermittent porphyria: Clinical report of four cases and review of literature. (http://www.ncbi.nlm.nih.gov/pubmed/20859493) Differential diagnosis of acute abdominal pain - acute intermittent porphyria. (http://www.ncbi.nlm.nih.gov/pubmed/21849959)

A 36-Year-Old Woman Comes to the Physician Because of Abdominal