Overview
Definition:
Superior Mesenteric Artery (SMA) Syndrome, also known as Wilkie's syndrome, is a rare gastrovascular disorder characterized by extrinsic compression of the third (horizontal) portion of the duodenum by the superior mesenteric artery (SMA) originating from the aorta at a narrow angle, typically between the aorta and the superior mesenteric artery itself
This compression leads to partial or complete obstruction of the duodenum.
Epidemiology:
The exact incidence of SMA syndrome is difficult to determine due to underdiagnosis
It is more commonly seen in adolescents and young adults, with a female predominance
Risk factors include rapid weight loss, anatomical variations in SMA origin or its angle with the aorta, and prolonged immobilization
Conditions predisposing to SMA syndrome include anorexia nervosa, malabsorption syndromes, spinal cord injuries, prolonged bed rest, and significant abdominal surgery.
Clinical Significance:
SMA syndrome can lead to significant morbidity, including malnutrition, dehydration, electrolyte imbalances, and gastric stasis
Unrecognized or inadequately managed cases can progress to severe complications like peptic ulcer disease, gastrointestinal bleeding, and even intestinal perforation
Definitive diagnosis and appropriate surgical intervention are crucial for long-term patient well-being and resolution of symptoms, making it a critical topic for surgical residents preparing for their examinations.
Clinical Presentation
Symptoms:
Postprandial epigastric pain
Nausea and vomiting, often bilious and projectile, occurring after meals
Abdominal distension
Early satiety
Weight loss and anorexia
Constipation or obstipation in severe cases
Mimics peptic ulcer disease or gastric outlet obstruction.
Signs:
Cachectic appearance in chronic cases
Abdominal tenderness, particularly in the epigastrium
Visible peristaltic waves in the upper abdomen
Abdominal bruits are uncommon but may be present
Bowel sounds may be hyperactive or hypoactive depending on obstruction severity.
Diagnostic Criteria:
No single definitive diagnostic criterion exists
Diagnosis is typically made based on a combination of clinical suspicion, characteristic radiological findings, and exclusion of other causes of upper GI obstruction
Key features include postprandial symptoms and evidence of duodenal compression by the SMA on imaging, with relief after alleviating the extrinsic pressure or altering body position.
Diagnostic Approach
History Taking:
Detailed history of weight loss, dietary habits, and precipitating factors like illness or surgery
Characterization of pain (onset, duration, triggers, relievers)
Nature of vomiting (frequency, content)
Previous GI complaints and treatments
Red flags include rapid progressive weight loss and severe postprandial distress.
Physical Examination:
Thorough abdominal examination, assessing for distension, tenderness, and palpable masses
Auscultation for bowel sounds and bruits
Assessment of hydration status and nutritional status
Digital rectal examination to rule out distal obstruction.
Investigations:
Upper gastrointestinal (UGI) series with barium or water-soluble contrast is often the initial investigation of choice
it can demonstrate a dilated stomach and proximal duodenum with a narrowed third portion, typically with a characteristic "beaked" appearance
The " ketiga" sign (third portion obstruction) is key
Gastroduodenoscopy can assess for intrinsic mucosal lesions but may not always visualize the extrinsic compression effectively
CT scan with oral and IV contrast is crucial for definitive diagnosis, accurately depicting the angle and narrowness of the SMA origin, the aortomesenteric distance (typically <25 mm, with a <10 mm increase upon abdominal extension), and the degree of duodenal compression
MRI angiography can also provide detailed vascular anatomy
Laboratory tests include complete blood count, electrolytes, renal function tests, and nutritional markers.
Differential Diagnosis:
Peptic ulcer disease with gastric outlet obstruction
Gastric malignancy
Crohn's disease affecting the duodenum
Superior mesenteric artery aneurysm
Intrinsic duodenal obstruction (e.g., stricture, tumor)
Intestinal malrotation
Functional gastric stasis
Bouveret's syndrome.
Management
Initial Management:
Conservative management is the first-line approach, especially in patients with mild symptoms or reversible causes of weight loss
This includes nutritional support with high-calorie, high-protein, low-fat diet
nasogastric decompression to relieve gastric distension
fluid and electrolyte correction
and treatment of any underlying conditions like anorexia nervosa
Jejunal feeding may be initiated to bypass the obstruction.
Medical Management:
Nutritional rehabilitation is paramount, often requiring parenteral nutrition or continuous enteral feeding into the distal small bowel (jejunum) to promote weight gain and allow for a decrease in the aortomesenteric distance
Pharmacological agents are generally not effective for the mechanical obstruction itself but may be used to manage associated symptoms like nausea and vomiting.
Surgical Management:
Surgical intervention is indicated for patients who fail conservative management, have severe symptoms, or have significant weight loss
The primary goal is to relieve the duodenal compression
\n**Surgical Options:**
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**Duodenojejunostomy:** This is the most common and effective surgical procedure
A side-to-side anastomosis is created between the distal duodenum and the proximal jejunum, bypassing the obstructed segment
This procedure has a high success rate and a low recurrence rate
\n2
**Gastrojejunostomy:** Less commonly performed than duodenojejunostomy, this procedure bypasses the obstruction by creating an anastomosis between the stomach and the jejunum
It is generally considered for patients with severe gastric dilation or when duodenojejunostomy is technically challenging
\n3
**Lysis of the Ligament of Treitz:** In some cases, division of the ligament of Treitz may release the traction on the duodenum, alleviating the compression
This can be performed alone or in conjunction with other bypass procedures
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**Laparoscopic Approach:** Minimally invasive techniques, including laparoscopic duodenojejunostomy, are increasingly being used and offer benefits such as reduced pain, shorter hospital stay, and faster recovery
\n5
**Open Surgical Exploration:** For patients with significant comorbidities or in whom laparoscopy is not feasible, open surgery is performed
The procedure involves dissecting the duodenum and creating the bypass
\n**Vascular Procedures:** In rare cases, when anatomical variations are severe, procedures like transposition of the SMA or division of peritoneal bands might be considered, but bypass procedures are generally preferred for their efficacy.
Supportive Care:
Close monitoring of fluid and electrolyte balance
Nutritional assessment and support throughout the perioperative period
Postoperative analgesia
Early ambulation
Management of potential surgical complications like anastomotic leak or ileus.
Complications
Early Complications:
Anastomotic leak or dehiscence
Ileus
Wound infection
Bleeding
Injury to adjacent structures (e.g., pancreas, mesenteric vessels).
Late Complications:
Recurrence of obstruction due to inadequate bypass or stenosis
Malnutrition and malabsorption
Dumping syndrome if gastrojejunostomy is performed
Adhesions.
Prevention Strategies:
Adequate nutritional rehabilitation before surgery
Careful surgical technique to ensure a tension-free anastomosis
Avoiding excessive mobilization of the duodenum
Proper patient selection for operative versus conservative management
Maintaining adequate hydration and early mobilization postoperatively.
Prognosis
Factors Affecting Prognosis:
Severity of malnutrition
Presence of underlying contributing conditions
Timeliness and appropriateness of surgical intervention
Success of the surgical procedure in relieving compression
Patient's overall health status.
Outcomes:
Surgical management, particularly duodenojejunostomy, generally yields excellent outcomes with significant symptom relief and restoration of nutritional status in most patients
Long-term prognosis is favorable with successful relief of the obstruction.
Follow Up:
Regular follow-up appointments to monitor weight gain, nutritional status, and any recurrent symptoms
Imaging studies may be performed if recurrence is suspected
Patients are typically advised to maintain a balanced diet and avoid precipitous weight loss.
Key Points
Exam Focus:
SMA syndrome is a mechanical obstruction of the third duodenum by the SMA
Key investigations are UGI series and CT scan
Treatment is primarily conservative with nutritional support
surgical bypass (duodenojejunostomy) is the definitive treatment for refractory cases.
Clinical Pearls:
Consider SMA syndrome in young, underweight patients with unexplained postprandial nausea, vomiting, and epigastric pain
The aortomesenteric distance is a critical radiological parameter
Always rule out underlying causes of weight loss.
Common Mistakes:
Delayed diagnosis due to misinterpretation of symptoms as peptic ulcer disease
Inadequate nutritional support in conservative management
Performing less effective bypass procedures when duodenojejunostomy is indicated
Not considering anatomical variants during surgery.