Introduction

Small-bowel perforation is a rare event that results from a number of different etiological causes. Causes include, trauma, infection, inflammatory bowel disease, foreign body ingestion, malignancy, iatrogenic causes and medical therapies for other diseases^1,2.

Although advances in the treatment and options for small-bowel perforations have occurred, the mortality rate can still be high. Orringer et al. and others report a mortality rate of between 28% and 42% during the 1970s^1,3 while Kan Tan et al. report a mortality rate of 19.1% in 2008². In addition, estimates of complications and morbidity post surgery have been as high as 76% ². Whilst prompt diagnosis and management is the gold standard, in reality, due to the geographical limitations in Queensland, Australia, this may not always be possible.

In view of the minimal analysis of this topic in the literature, this study was undertaken to analyse the incidence, patient characteristics, causes, morbidity and mortality associated with the management of small bowel perforations in a rural setting. This was accomplished by performing a retrospective analysis of all cases of small-bowel perforation treated in our institution. These cases included those that had presented primarily to the hospital in question and those that had been treated at an outlying hospital prior to transfer for definitive management.

These results were then compared to a 1,300-bed tertiary hospital in Singapore. Comparison was performed using a classification system of complications and the Mannheim peritonitis index, both of which had been previously ratified⁴. In addition, the distance from our centre and presentation to another smaller hospital prior to transfer was also evaluated in this study.

Materials and Methods

Toowoomba Base Hospital is a 280-bed public hospital located in the Darling Downs Health Service District of Queensland Health. It provides acute secondary care to a regional population of approximately 280,000 dispersed throughout South-West Queensland. It has a Level-two ICU, providing general and specialist surgical services. Due to its location it acts as the main referral centre for multiple smaller rural hospitals, many up to 1000 kilometres away.

A retrospective analysis of all patients diagnosed with a small-bowel perforation between September 2004 and September 2009 was performed. Patients were identified based on the Hospital’s diagnostic coding system and were then confirmed using operative records, diagnostic imaging reports and histopathology specimens.

Patients who had a clinical diagnosis of a full-thickness bowel wall ischaemia at time of surgery without histological perforation, anastomotic leak following previous operation or pneumoperitoneum without a documented source were all excluded from this review.

The decision for surgical intervention was based on clinical assessment, diagnostic imaging, patient and the treating Surgeon’s decision regarding treatment plan. All patients were fluid resuscitated, commenced on intravenous antibiotics and in several instances a nasogastric tube was inserted for decompression. Surgery, when indicated, occurred as an emergency case and was performed by or under the supervision of fellows of the Royal Australasian College of Surgeons.

During exploration, once the site of perforation was identified, operative management included a small-bowel resection, over-sewing of the perforation and/or formation of a stoma. Anastomosis following small-bowel resection was performed either as a hand-sewn or stapled anastomosis. A copious lavage was performed following closure of the perforation and prior to closing the laparotomy wound.

Data was collected on each patient including age at presentation, gender, existing co-morbidities, distance of residence from The Toowoomba Hospital, length of stay, type of management (operative and conservative), length of operation, site of perforation, complications, mortality and cause of perforation. Pre-operative biochemical markers and the American Society of Anaesthesiologists (ASA) score were also documented. To allow comparison with other published series, the severity of abdominal sepsis was graded using the Mannheim Peritonitis Index (MPI)⁴ with a score of >26 classified as severe. Given the parameters (Table 1), this index could only be applied to cases requiring operative intervention. Given that many patients were transferred from surrounding areas, pre-operative duration of peritonitis was determined by signs of peritonitis at the initial treating hospital. Organ failure was defined as kidney failure, pulmonary insufficiency, intestinal obstruction, and cardiovascular insufficiency. In addition, to allow comparison complications were graded according to a classification system proposed by Calvien et al.^5,6 (Table 2).

Given the small number of cases, categorical variables were analysed using Fisher’s exact test. P values <0.05 were considered significant and are all reported as two-sided calculations. Statistical analysis was performed using Graphpad Instat software v3.10 (San Diego, USA).

Results

Thirty-two patients were found to have a small-bowel perforation at Toowoomba Base Hospital during the period from September 2004 to September 2009. Of these, the vast majority 26 (81.3%) were treated with operative management, while only six (18.7%) were conservatively treated (Table 3). Of the total cohort of patients, 11 (34.3%) had presented to an outlying hospital and received treatment prior to being transferred to our hospital. The median distance in kilometres from the patient’s residence to Toowoomba Hospital was 21.5 kilometres with a range of 0-1422 kilometres. Over half (71.9%) of all the patients lived within a 100-kilometre radius from Toowoomba Hospital.

The age of the total population cohort studied ranged from 8-92 years with a median age of 44.5 years. Subgroup analysis revealed a median age of 37 years for all surgically treated small-bowel perforations, 69 years for surgically managed non-traumatic small-bowel perforations and 60 years for conservatively managed small-bowel perforations. (Table 3)

The overall mortality of our total cohort was two patients (8.33%) with one patient undergoing surgical management and the other undergoing radiologically-guided intervention. Both of these mortalities occurred in patients that resided within 100 kilometres of the hospital with one being treated at another hospital prior to transfer. There was found to be no significant differences in mortality or grade of complications between those living within 100 kilometres and those living greater than 100 kilometres from Toowoomba Hospital. (Table 4)

The median length of admission for the total cohort of small-bowel perforations was 11.5 days with a range of 1-47 days with the highest length of stay in the group treated with surgery for a spontaneous perforation compared to those with a traumatic perforation and those treated conservatively (18, 6.5, 5.5 days, respectively.)

The largest causative mechanism of small-bowel perforation in our total population was non-surgical trauma (n=8, 25%) followed by ischaemia caused by vascular insufficiency secondary to adhesions (n=6, 18.8%). Other causative mechanisms included, iatrogenic injury (n=4, 12.5%), small bowel diverticula (n=3, 9.4%), carcinoma (n=2, 6.3%), adhesions (n=2, 6.3%), perforation of a Meckel’s Diverticulum (n=2, 6.3%) and ingested foreign bodies (n=2, 6.3%).

Six patients (18.8%) had no imaging performed by our department, all of which were involved a significant trauma or had suffered a recognized iatrogenic perforation. Of those that had a CT scan or X-ray, 16 (50%) were seen to have a pneumoperitoneum, one (3.1%) had an ileus and one (3.1%) had an abscess.

Analysis of the conservatively treated population

Six patients were treated with conservative management in our total population. Management in this population consisted of intravenous antibiotics, fluid resuscitation and regular monitoring for deterioration. In four patients (66.6%), the patient underwent aspiration of intra-abdominal collections with the guidance of imaging. The decision for conservative or surgical management was based upon the clinical status of the patient, biochemical markers, mechanism of perforation and the surgeon’s management plan in relation to futility of surgical intervention.

Half (n=3, 50%) of the patients treated with conservative management were diagnosed with a small-bowel perforation secondary to small-bowel diverticulitis. Sixty-six percent (n=4) had been treated at another hospital for an unknown period prior to arrival at Toowoomba Base Hospital. Despite previous intravenous treatment, eighty-three percent (n=5) still had marked leukocytosis with only one patient having a temperature greater than 38 degrees on arrival at Toowoomba. One patient had severe hyponatraemia (124 mmol/L) but all patients were found to have an albumin level of <35g/L. All patients appeared to be adequately fluid resuscitated with no patients having a systolic blood pressure <90mmHg.

There was one mortality in the patients treated by conservative management: an 85-year-old male with end-stage Parkinson’s disease, bed ridden and with poor quality of life, who was non-communicable and fully dependent. CT confirmed a perforated viscus and he was treated non-operatively with palliative intent.

Analysis of the surgically treated population

Spontaneous perforations

Traumatic Perforations

There were eight reported cases of traumatic small-bowel perforation found during this period. Of these, the vast majority (n=6, 75%) were as a result of a motor-vehicle accident with the remaining two as a result of stab wounds. All patients in this subset were treated with surgical intervention via a laparotomy with oversewing of the perforation, the treatment of choice in over half of the patients (57.1%). Seven of the eight traumatic perforations were found to be in the jejunum at the time of operation.

The average length of stay of this population was 7.25 days while the median Mannheim Peritonitis Index for these patients was 7.4. All patients recovered completely with only 1 patient having a Grade-1 complication.

Figure 1

Table 1: Mannheim Peritonitis Index

Figure 2

Table 2: Classification of Surgical Complications by Calvien et al.

Figure 3

Table 3: Demographics of small bowel perforations and comparison to patients treated at Tan Tock Seng Hospital.

Figure 4

Table 4: Subgroup analysis of outcomes for patients with any small-bowel perforation based upon distance of residence from Toowoomba Base Hospital

Figure 5

Table 5: Causes of non-traumatic small-bowel perforations treated surgically and comparison to patients treated at Tan Tock Seng Hospital

Figure 6

Table 6: Patient characteristics and outcomes of surgically managed patients with a non-traumatic small-bowel perforation

Figure 7

Table 7: Admission clinical parameters of total patients treated with surgery in study groups

Discussion

Whilst the Mannheim Peritonitis Index has been adopted in other hospitals due to the ease of application and reflection of the prognosis of patients^2,7, it is not routinely used at The Toowoomba Base Hospital (TBH). Although more recently other classifications systems have been proposed⁵, the Mannheim Peritonitis Index was used to allow ease of comparison. Interestingly, there was no reported significant difference in the MPIs of patients treated for a spontaneous small-bowel perforation at Toowoomba Hospital when compared to those treated at Tan Tock Seng Hospital. This might have been different if the MPI had been calculated for the total cohort surgically treated at Toowoomba hospital (i.e. including those treated for a traumatic perforation).

Obviously patients involved in trauma usually would have a lower MPI as a result of many factors. These include, age of patients and the quick presentation of trauma to a hospital therefore scoring less by the MPI scale. Given that ‘the golden hour’ is often quoted as optimal treatment in trauma, patients usually will not have peritonitis for >24 hours and are less likely to have a faecal exudate.

Although six patients did not have any imaging performed at Toowoomba prior to theatre, we believe that the actual number without imaging would be much less than this. Our patient population included one patient 1422 kilometres from The Toowoomba Base Hospital. Given therefore that in some of these situations, the Toowoomba Base Hospital would not be the first hospital patients presented to, we believe many patient would have at least had an erect chest x-ray at these outlying hospitals. Unfortunately, though, we are unable to confirm this as there is no record of external images on our internal imaging system. We believe in cases where intra-abdominal viscus perforation is suspected, and the patient is haemodynamically stable, CT should be used to help identify the site and exclude other acute abdominal conditions.

Although the role of systolic hypotension has also previously been investigated on the effect on complications², we were unable to perform the same analysis. Many of these remote hospitals often attempt to stabilise the patient with adequate fluid resuscitation prior to transfer. Therefore, blood pressure on arrival to Toowoomba Hospital may not reflect the status of the patient on presentation to medical care. We believe the haemodynamic and biochemical stability of patients treated at Toowoomba Hospital in part reflects the adequate resuscitative efforts of outlying hospitals prior to transfer.

Interestingly, there was no significant difference in mortality or type of complication in patients living >100 kilometres from TBH when compared to those living within 100 kilometres. This illustrates the importance of adequate stabilisation and early commencement of antibiotics although results may not be an adequate reflection given the small numbers studied. In a study of perforating small-bowel injuries in children, performed by Thompson and Holland, a delay in diagnosis and treatment was not found to considerably affect the complication rate or length of admission⁸.

While no infective causes of small-bowel perforation were identified in our series, this probably reflects the incidence of these diseases in Australia. Interestingly, when examining other published series, it has been suggested the different causative mechanisms may be related to geography, economics and possibly culture¹. For example there were no cases of tuberculosis-related bowel perforation in our study group compared to 10% of cases in Tan Tock Seng².

The incidence of small-bowel diverticulosis is estimated to be between 0.06% and 1.9% with the majority of people being asymptomatic^9,10. While diverticula can occur at any place along the small bowel, 45% are thought to occur in the duodenum. Perforation of a small bowel diverticulum occurs in less then 3% of cases and can be precipitated by infection and stasis, blunt trauma and foreign body impaction⁹. Despite estimated mortality rates of 21-42% for small-bowel diverticula perforations, we recorded no mortalities with either a conservative or operative approach although once again we recognize the impact of small numbers studied. Although perforation of a diverticulum is classified as a rare complication of diverticulosis, surprisingly our cohort included four patients with a perforation who were managed conservatively.

It is interesting to note that two cases of small-bowel perforation from a foreign body were reported in our series. Estimates of the mortality associated with foreign-body ingestion report that approximately 1500 fatalities occur every year in the United States as a result of complications including perforation^11,12. Ingested foreign bodies will pass through the gastrointestinal tract spontaneously in 80-90% of cases with the rest requiring endoscopic retrieval^13,14,15 or surgical intervention. One of our documented cases was found to be from accidental ingestion of a bread clip with the other arising ten years after deliberate ingestion. Interestingly, in retrospect, the patient probably had presented previously due to a micro-perforation, but on investigation of each episode, no pneumoperitoneum was seen and a conservative approach was undertaken. Diagnosis of foreign body ingestion can often be more difficult in the obese patient and psychiatric patient leading to delayed treatment and possible mortality^14,15. Given the risks of surgical intervention, controversy exists around the management of foreign-body ingestion and management is influenced by time since ingestion, age, clinical symptoms and type of foreign body.^{12, 13, 14}

Although inflammatory bowel disease is known to be a common cause, in our review only 1 case was recorded as being causative^1,2. In a review by Orringer et al. of 19 spontaneous small-bowel perforations, the cause was found to be inflammatory bowel disease in 21% of cases¹. Controversy currently surrounds early aggressive surgical management of the diseased segment or persisting with non-surgical treatment until clinically indicated^2,16. Surgical resection was completed in our one patient after medical therapy had failed. We would emphasise in our experience that good outcomes are related to good management and subsequently low complication rates.

Conclusion

Despite different mechanisms of pathology, patients treated in rural and non-tertiary hospitals can still have acceptable outcomes and rates of complications when compared to large tertiary referral centres. We believe adequate initial management by smaller more rural hospitals plays an integral part in the management of patients with an acute abdomen in rural Australia.