Freeze-dried vs Fresh Fecal Microbiota Transplantation in Patients With Slow Transit Constipation

Inclusion Criteria: Chronic constipation according to Rome III criteria, defined as two or fewer spontaneous, complete bowel movements (SCBMs) per week for a minimum of 6 months; Age ≥ 18 years; BMI: 18.5-25 kg/m2; Slow colonic transit confirmed by colonic transit test (colonic transit time (CTT) \> 48 hours); Normal anorectal manometry, with no evidence of dyssynergia and confirmed ability to expel rectal balloon; No radiographic evidence of functional (i.e. pelvic floor dyssynergia) or anatomical (i.e. significant rectocele and intussusception) impediment to the expulsion of the radio-opaque contrast; Disease duration \> 1 year; Traditional treatment with dietary modification, laxatives (including osmotic and stimulant laxatives), and biofeedback tried over the past 6 months without success; Exclusion Criteria: Bowel constipation due to innate factor (i.e. megacolon) or secondary interventions (i.e. drugs, endocrine, metabolic, neurologic or psychologic disorders); History or evidence of gastrointestinal diseases (i.e. obstruction, cancer, inflammatory bowel diseases) ; Previous abdominal surgery, except cholecystectomy, appendicectomy, tubal ligation and cesarean section; Previous proctological or perianal surgery; A constipation condition meeting the Rome III criteria for IBS or functional abdominal pain syndrome; Pregnant or breast-feeding women; Infection with enteric pathogen; Usage of probiotics, prebiotics and/or synbiotics within the last month; Usage of antibiotics and/or PPIs within the last 3 months; Smoking or alcohol addiction within the last 3 months; Uncontrolled hepatic, renal, cardiovascular, respiratory or psychiatric disease; Disease or therapy with drugs (i.e. antidepressants, opioid narcotic analgesics, anticholinergics, calcium antagonists, nitrates, antimuscarinics) that, in the opinion of the investigator, could affect intestinal transit and microbiota.