Our patients have a good functional outcome compared to the literature (see section 1.7.1). As we had updated information from the medical files of all patients, we know that only one out of 103 had the pouch removed due to recurrent malignancy. No pouch has been removed or defunctioned for any other reason and only a few patients experienced short- and long-term septic pelvic complications. The complication and failure rate is the same or slightly lower than reported in the literature (see section 1.6). These good results may be due to a number of factors. All patients were defunctioned with a loop-ileostomy, diminishing the clinical
consequences of anastomotic leakage and septic complications, which is associated with poor function. Additionally, there have been four dedicated senior consultant surgeons in the pouch team during the study period, two of whom were trained in pouch surgery elsewhere. At least two of the four have been present at every operation, enabling continuity and standardisation of the surgical technique. In recent years, the pouch team has performed over 10 pouches per year, as recommended by the 2015 ECCO guidelines36. An IBD multidisciplinary team has been established, and all patients were cared for on the same ward. We have skilled ward nurses and scrub nurses familiar with IPAA and stoma nurses attending patients before leaving the hospital.
We found patients with higher PFS to have poorer QoL, with a PFS ≥ 8 to be the best cut-off to predict when pouch function is so poor it impaires QoL. This is in accordance with a study by Berndtsson et al107. We also found poor pouch function to be correlated to impaired sexual
function in women, however we did not find the same correlation in men. It might be that female sexual function is more susceptible to reduced pouch function (especially fecal incontinence), and that there is a weaker correlation in men that our study was underpowered to find. These findings indicate that even small changes in bowel habit lowering the PFS can significantly influence a patient’s quality of life and sexual function.
When doing manovolumetric examinations, we found a significant difference in pouch volume at al sensation thresholds between well and poorly functioning pouches, with volume at urge explained 38% of functional outcome. Pouch volume was correlated to number of bowel movements, but the meaning of this finding is unclear as patients with a high number of bowel movements will perhaps not distend their pouch, and hence the volume will not increase. A surprising finding was that sensation thresholds were triggered by pouch pressure and not by pouch volume, with no difference in pressures at sensation thresholds between the groups. According to LaPlace’s law, wall tension in predefined pressures should be lower in smaller pouches. An explanation might be greater wall stiffness in the small pouches, possibly due to fibrosis or inflammation after pouchitis and/or septic pelvic complications. This is supported by our finding of a higher prevalence of histological signs of inflammation in the poorly functioning group, and better compliance in the well functioning group at lower
pressures. Better compliance might be due to a lower wall tension at moderate filling volumes, and might in itself be a contributor for their better function. It is further supported by the higher prevalence of septic pelvic complications, pouchitis episodes and perianal disease among the poorly functioning pouch patients. It is likely to think the mentioned complications can contribute to a stiffening of the pouch, resulting in reduced compliance and smaller volumes, which reduces the functional outcome. Surprisingly, we did not find any
correlations between pouch function and calprotectin levels, hence this is not a good measure to predict functional outcome in patients with IPAA. We found hand-sewn anastomosis to be negatively correlated to function, which is consistent with the literature. This might be due to increased tension in the more distally placed hand-sewn anastomosis.
We failed to find any significant difference in QoL or functional outcome between J and K patients, although K patients scored slightly better in most domains. However we found K pouches to have a significantly larger pouch volume at all sensation thresholds. Other studies have also found K pouches to have a larger volume than J pouches. This is probably found in the difference in pouch formation, as the more spherical K-pouch gives a larger pouch volume than the cylindrical J pouch constructed with the same length of ileum. The literature is not conclusive regarding which pouch design gives the best functional outcome, however there is consensus around the significance of volume (see section 1.7.2). As K pouches give a larger volume than J pouches, and volume is positively correlated to function, all patients in our unit are given a K pouch. However, pouch design is not the only factor determining pouch volume, as pouches with same design constructed of same length of ileum is known to have a
significant variation in volume45, which was also confirmed by our study. The reasons as to why volume varies extensively in pouches, while they supposedly are made of the same lengths of ileum, are not known. In addition to the possibility of septic pelvic complications and/or chronic pouchitis causing fibrotic tissue in the pouch, resulting in stiffening of the wall and smaller volumes, one might speculate that factors like the diameter of small intestine and anatomical characteristics of the pelvis may also be of some relevance for volume. However we did not find a correlation between total pelvic volume on MRI and pouch volume at urge, although some transverse bony limitations were correlated to urge volume. It is possible the
pelvic width is somehow correlated to pouch volume, however the significance of this finding is unclear.
MRI has not been used routinely as a diagnostic tool to investigate pouch function, and its value in diagnosing mechanisms for malfunction is unclear149,150. Our study is the first to our knowledge comparing findings between well and poorly functioning pouches and hence establishing a reference for normal findings in pouch patients. We found no significant differences in morphological findings, nor difference in functional MRI results, between the well and poorly functioning pouches. Neither did we find any radiological findings correlated to emptying difficulties, urge or soiling. The majority of patients had one or more signs of inflammation on MRI, and it is important to note this seems to be a normal finding also in well functioning pouches. No morphological finding of inflammation was correlated to histological signs of acute inflammation, and only pouch wall thickness was correlated to PDAI scores. Other studies have found MRI findings of inflammation to have a strong
correlation with endoscopic findings but not with histological findings151,152, however in these studies intravenous contrast was given. Hence it seems MRI without intravenous contrast is not suited to diagnose pouchitis. We were unable to quantify the evacuation fraction, as we did not have a reliable measure of the amount of emptied gel. Previous studies have reported a wide range in evacuation fraction (28-77%)109,149,153-155, with a recent study finding patients with more than 33% barium retention complaining of incomplete emptying149.
Lastly the importance of microbiota for pouch function is a promising research field which this thesis has not touch upon. During the study period faecal samples for microbiotic analysis was gathered, however the results are not yet analyzed.