Teaching Case

Sudden lumbar and abdominal pain without vomiting, changed bowel habits, abnormal vital signs and peritonism for a few hours. Medical history included hypertension, resection of early-stage breast cancer, a similar self-limiting episode of abdominal pain two years earlier which resolved without specific treatment.
All routine laboratory tests were within normal limits.

Pain was unresponsive to usual painkiller medications.
Urgent multidetector CT (Fig. 1) excluded abnormalities of abdominal organs and bowel. Increased “misty” attenuation of the retroperitoneal and coeliac fat planes was noted, plus moderate bilateral fascial effusions. Coronal images (Fig. 1f, g) depicted the extent of retroperitoneal oedematous changes surrounding the vessels without mass effect, perceptible enhancing walls and solid tissue.
Despite absence of facial or superficial swelling, clinical suspicion of vasogenic oedema led to withdrawal of angiotensin-converting enzyme (ACE) inhibitor medication (enalapril) and treatment with bradykinin-receptor agonist icatibant with prompt clinical relief.
Within one week, repeated CT (Fig. 2) and MRI (Fig. 3) including fluid-sensitive fat-sequences showed prompt regression of retroperitoneal changes, without appreciable abnormalities of the abdominal viscera, particularly indicating pancreatitis. Further laboratory tests, including normal C1-C3-C4 complement assays excluded a hereditary form of angioedema.
Within the next year, the patient experience two bouts of visceral angioedema with identical clinical and imaging features.

Clinically, angioedema is defined by episodic transient oedematous swelling affecting any single part of the body or multiple sites simultaneously, most commonly superficial regions in the face, neck and upper airways, genitals, and extremities. Symptoms of angioedema typically worsen over 24-36 hours and resolve over the next 2-3 days. In predisposed individuals, acquired angioedema is triggered by medications, allergens, pressure or cold: the majority of cases are related to angiotensin-converting enzyme (ACE) inhibitors, since ACE degradates bradykin, which causes vasodilatation and increased vascular permeability. Angioedema affects 0.1-1% of patients receiving ACE-inhibitor medications, most usually within a few weeks or months after treatment start. The much rarer, autosomal-dominant hereditary angioedema shares analogous clinical features and is caused by deficiency or inactivation of C1-esterase inhibitor in the complement system [1, 2].
A rare manifestation of both hereditary and acquired angioedema, visceral angioedema (VAE), involves the abdominal viscera without cutaneous involvement, and manifests as acute-onset or recurrent, mild to severe cramping abdominal pain, distension and tenderness, nausea or vomiting. In most patients investigated with CT, VAE appears as unspecific small bowel mural thickening with stratified “water halo” appearance due to the low-attenuation oedematous submucosa between enhancing mucosal and serosal layers, mesenteric oedema and free fluid. The dominant feature in this patient, retroperitoneal oedema has been sometimes reported as an associated finding [3-6].
Diagnosis of ACE-induced angioedema is confirmed by symptom relief within 24-48 hours after drug discontinuation. Treatment includes intravenous fluids to battle hypovolaemia from fluid extravasation, and use of the recently approved drugs respectively blocking C1-esterase and kallicrein. Angioedema does not respond to epinephrine, antihistamines or steroids [1, 2].
Often mimicking an acute abdomen, VAE should be considered in the differential diagnosis of abdominal pain, particularly in patients on ACE-inhibitors and with history of repetitive self-limiting episodes. Unfortunately, poor physicians’ awareness of the disease and overlapping signs and symptoms with other medical conditions can lead to substantial diagnostic delays or ineffective therapies [1, 2].
In patients with known AE suffering from abdominal pain, multidetector CT represents the imaging modality of choice to assess visceral involvement. Differential diagnosis includes other causes of stratified small bowel thickening (such as ischaemia, vasculitis, Crohn’s disease, infectious or radiation enteritis) and of mesenterial, omental and retroperitoneal fluid extravasation. Correct diagnosis and imaging confirmation of prompt regression of changes allows to avoid confusion with abnormal collections and obviate unnecessary drainage or surgery [1, 3-8].