What is SMIDT (Small Intestine Dysmotility) syndrome?

What is Small Intestinal Dysmotility Syndrome?

Small intestinal dysmotility syndrome is a chronic disorder characterized by failure of coordinated intestinal propulsion that produces symptoms and signs of intestinal obstruction (colicky abdominal pain, nausea, vomiting, abdominal distension, and dilated bowel) without any mechanical obstructing lesion. 1

Core Definition and Clinical Presentation

Small intestinal dysmotility occurs when the intestine fails to propel luminal contents effectively despite the absence of an organic obstructing lesion. 1 The condition is considered severe when it causes malnutrition (BMI <18.5 kg/m² or >10% unintentional weight loss in 3 months), dehydration, or electrolyte disturbances requiring nutritional or fluid support. 1

Key Clinical Features:

• Symptoms persist for more than 6 months (defining chronicity) 1
• Colicky abdominal pain, nausea, and vomiting with abdominal distension 1
• Dilated bowel on imaging without mechanical obstruction 1
• Frank obstructive picture is not always present, especially with neurological etiologies 1

Pathophysiological Classification

The disorder results from abnormalities in intestinal smooth muscle function influenced by neural and humoral factors. 1 Three major histopathological entities are recognized: 1

Primary Categories:

• Myopathies: Predominant involvement of smooth muscle cells, characteristically associated with massive gut dilatation 1
• Neuropathies: Predominant involvement of enteric neurons, more common overall in causing small bowel dysmotility 1
• Mesenchymopathies: Involvement of interstitial cells of Cajal (ICC), the gut pacemakers 1

Neuropathies are more common than myopathies in causing small bowel dysmotility overall, but myopathies may predominate in chronic intestinal pseudo-obstruction (CIPO). 1

Chronic Intestinal Pseudo-Obstruction (CIPO)

CIPO represents the most severe form of small intestinal dysmotility, characterized by chronic or intermittent symptoms and signs of (sub-)ileus despite absence of intestinal obstruction. 2 This is a rare, complex disorder at the extreme end of the dysmotility spectrum. 3

CIPO Characteristics:

• Failure of intestinal tract to propel contents 3
• Signs and symptoms of bowel obstruction without any obstructive lesion 3
• May require permanent parenteral nutrition in severe cases 2
• Small bowel transplantation can be considered as ultima ratio if parenteral nutrition causes intolerable complications 2

Diagnostic Challenges

The diagnosis is often empirical, especially when there is no definite histological confirmation of disease process. 1 Clinical features, investigation results (manometry), and histology may not combine to indicate one specific diagnosis. 1

Important Diagnostic Considerations:

• Small bowel manometry is the preferred diagnostic method, particularly for patients with severe and progressive symptoms 4
• Diagnosis requires exclusion of mechanical obstruction 5
• Assessment of motor function by measurement of transit and intestinal pressure profiles 5
• If uncertainty exists, document as "working diagnosis" (probable or possible) rather than giving definitive diagnostic label prematurely 1

Common Pitfalls:

A premature or erroneous organic diagnosis in those with predominantly psychosocial issues or abnormal illness behavior may make management of contributing issues very difficult. 1 It is very difficult to remove a diagnostic label once given. 1

Contributing and Aggravating Factors

Multiple factors can give rise to or aggravate the clinical picture: 1

Medication-Related:

• Opioids inhibit intestinal motility and invalidate tests of small bowel motility 1, 6
• Drugs with anticholinergic effects (including cyclizine) 1
• Calcium channel blockers 1
• Antipsychotics, especially clozapina and phenothiazines 7

Metabolic and Endocrine:

• Hypokalaemia 1
• Hypothyroidism 1, 7
• Diabetes mellitus through autonomic neuropathy 7

Surgical and Structural:

• Previous abdominal surgery and adhesions 1
• Multiple laparotomies can result in secondary dysmotility 7

Neurological Conditions:

• Parkinson's disease 7
• Brainstem lesions, spinal cord injury, multiple sclerosis 7
• Autonomic neuropathy 7

Other Factors:

• Sepsis 1, 7
• Psychosocial problems including abnormal illness behavior 1
• Malnutrition itself 1

Overlap with Functional Gastrointestinal Disorders

Differentiation from functional gastrointestinal disorders (irritable bowel syndrome, functional dyspepsia, functional bloating) is difficult. 1 These conditions share many symptoms with small intestinal dysmotility. 1

Critical Distinction:

Significant malnutrition is rarely a consequence of functional gastrointestinal disorders. 1 Significant caution should be exercised to avoid escalating to more invasive forms of nutrition support in patients with functional symptoms, especially in pain-predominant presentations, in the absence of objective features of biochemical disturbance or those with high or normal BMI. 1 Such escalation carries risks of iatrogenesis and does not appear to improve global function, quality of life, or symptoms in clinical practice. 1

Management Principles

General therapeutic goals include: 2

• Maintenance of adequate nutritional status 2
• Improvement of propulsive motility 2
• Amelioration of abdominal symptoms 2
• Avoidance and/or therapy of complications 2

At present, nutritional support, symptom management, and avoidance of long-term complications are the mainstay of treatment. 3 Several novel pharmacological agents hold promise including gastrointestinal hormone agonists and prokinetics. 3

Management Requires Multidisciplinary Team:

Gastroenterologist, gastrointestinal physiologist, gastrointestinal surgeon, pain team, psychiatrist/psychologist, rheumatologist, urologist, gynecologist, neurologist, clinical biochemist, histopathologist, radiologist, and nutritional support team. 1