Postoperative ileus and gastrointestinal complications following spine surgery: A systematic review of incidence, risk factors, prevention, and treatment

Abstract

Postoperative Ileus (POI) and other gastrointestinal (GI) complications comprise a significant portion of medical complications seen in spine surgery patients. Experts hypothesize that ileus can occur due to a combination of anesthetic agents, opioid-induced intestinal dysmotility, and decreased mobility. POI and GI complications lead to longer lengths of stay, increased hospital costs, and increased risk of readmission and reoperation in spine surgery patients. A systematic review of the literature was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. 59 primary articles met the inclusion criteria. The reported incidence of POI following spine surgery varied significantly from 0.2% to 35.4%, with the middle 50% of studies ranging from 5.1% to 13.6%. Cumulative GI complication rates ranged from 2.1% to 16.2%, with more severe pathologies such as acute colonic pseudo-obstruction (ACPO) having expectedly low incidences of <1%. Conclusions regarding potential risk factors were highly variable. Male sex, increased levels fused, and lumbar level fusions were the only unanimous variables. Intraoperatively, increased surgical time, certain intraoperative opioids (remifentanil, sufentanil), and increased opiate dosages are associated with increased rates of ileus. Early feeding as a prevention strategy has demonstrated variable efficacy, while early mobilization and gum-chewing have been shown to stimulate bowel function. If ileus does occur, symptoms typically resolve with conservative management including NPO, intravenous fluid maintenance, electrolyte replacement, laxatives, and adding nasogastric suctioning when bloating and nausea are more severe. If patients fail conservative treatment, physicians can add promotility agents such as neostigmine. The incidence of POI after spinal surgery is high. Identification and appropriate mitigation of risk factors, as well as early ambulation for prevention and early recognition for treatment are important in the event of ileus.

INTRODUCTION

Improved techniques, enhanced outcomes, and longer life expectancies have contributed to an increase in the number of patients receiving spinal surgery annually.[1,2] However, due to their complexity, spine surgeries can be associated with high complication rates. Longer and more invasive operations, such as multilevel fusions and adult spinal deformity (ASD) surgeries, are associated with complication rates ranging from 21.6%–25.4%.[2,3,4]

Gastrointestinal (GI) complications comprise a significant portion of medical complications seen in spine surgery patients.[5] These complications can range from relatively benign to life-threatening in rare situations.[6] These pathologies include ileus, pancreatitis, GI bleed, dysphagia, cholecystitis, superior mesenteric artery (SMA) syndrome, and acute colonic pseudo-obstruction (ACPO).[6,7] Postoperative ileus (POI) is often cited as one of the most common complications overall in patients after spine surgery.[8,9,10,11] POI is characterized by a temporary cessation of GI peristalsis resulting in intestinal dilation.[12,13] Of all types of orthopedic surgeries, rates of ileus, including severe ileus, are highest in spine procedures.[14,15] Although the mechanism of ileus is not completely elucidated, experts hypothesize that it is likely multifactorial, with anesthetic agents, opioid-induced intestinal dysmotility, and decreased mobility leading to an imbalance in sympathetic drive.[16,17,18,19] Given that spine surgery involves a significant pain burden and often high opioid use, it is understandable why ileus and GI complications are so prevalent in spine surgery patients.

Patients often suffer from some degree of GI dysmotility, ranging from simple constipation to more severe obstruction in rare situations, such as in SMA syndrome and ACPO. Many perioperative medications-opiates, antacids, anticholinergics, antidepressants, antihistamines, CCBs, clonidine, diuretics, iron, psychotropics, sympathomimetics – can promote constipation.[6] Although rare, SMA syndrome is a GI obstruction due to a compression of the third part of the duodenum, and if not treated promptly, it can be life-threatening.[6] ACPO, aka Ogilvie’s syndrome, is characterized by marked distention of the cecum and transverse colon without mechanical obstruction.[16] Prolonged ileus can be caused by ACPO but differs slightly due to involvement of the small intestine and colon.[6,20] Even though ACPO is uncommon, it should be included in the differential diagnosis because, if unrecognized and untreated, it can result in cecal perforation in as many as 20% of cases with mortality rates of 25%–60%.[21,22]

In addition to being a significant barrier to effective pain management and postoperative recovery,[21] POI and GI complications lead to longer lengths of stay, increased hospital costs, and increased risk of readmission and reoperation in spine surgery patients.[16,17,23,24,25,26,27,28,29,30,31] Despite these challenges, spinal surgery patients who experience GI complications can still experience comparable long-term improvements in pain and function compared to those without complications.[2,7,32] It is imperative to identify risk factors and prevention techniques to improve patient outcomes and provide significant cost savings.[33] To our knowledge, this is the first review integrating all aspects of care, including incidence, risk factors, prevention, and treatment of ileus and GI complications in spine patients.

METHODS

A search of PubMed publications through June 2024 was completed in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [Figure 1]. Search terms included “adult spinal deformity,” “spine surgery,” “ileus,” “postoperative ileus,” “nausea,” “gastrointestinal,” “prevention,” and “treatment.” Different combinations of search terms and Boolean operators were used to maximize search sensitivity.

Figure 1.

The Preferred Reporting Items for Systematic Reviews and Meta-analyses flow diagram of included studies

Inclusion criteria included original studies that reported on POI and GI complications following adult spine surgery. Exclusion criteria included non-English studies, patient populations <18 years old, and studies that included spine surgeries for trauma and tumors.

One reviewer initially screened article titles and abstracts for potential eligibility. Once articles were excluded by title and abstract, full-text articles were screened for inclusion and exclusion criteria. References of included articles were manually screened to identify additional studies. From each full-text article that met the inclusion criteria, the following data points were extracted: study title, authors, publication year, study design, level of evidence (per Oxford criteria), study population parameters, number of levels fused (if applicable), complication rates, risk factors, prevention, and treatment recommendations.

RESULTS

From the initial search, 845 records were identified from PubMed, and 187 duplicates were removed. Of the remaining 658 articles, initial abstract screening identified 151 full-text studies. After full review, 59 primary articles[1,5,7,8,9,10,11,14,15,16,17,18,20,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67] were determined to meet all the inclusion criteria and were used for data analysis [Figure 1]. Demographics and major results from the included studies are summarized in Table 1.

Table 1.

Risk factors for postoperative ileus

Postoperative Ileus
Patient Characteristics
Risk Factor	Positive Studies
Male Sex	[9,36,37]
Electrolyte/Fluid Disorder	[22,36]
Comorbidities
History of Substance Use	[17,36]
Hepatobiliary disease	[17,18]
GERD	[31,73]
Surgical Variables & Approaches
Risk Factor	Positive Studies
Increased Surgical Time	[18,23,29,37,44]
Multilevel Fusion	[17,18,28,36,44,45,46,71]
Lumbar Level	[31,45]
Anterior Approach	[11,36,47,48]
Intraoperative Repositioning	[51,52,72]
Increased Opioid Dosage	[17,18,43]
Remifentanil	[17,43]

Incidence

Most studies reported on POI or GI complication incidence after spinal surgery]. Of the 39 articles that reported on POI incidence, rates varied significantly from 0.2% to 35.4%. The middle 50% of studies ranged from 3.13% to 10.50% and the largest study[23] reported a rate of 7.4%. Given the low incidence of individual GI complications, most studies grouped these complications in their analyses. Of the 10 articles that reported on GI complication rate, the middle 50% of studies ranged from 3.45% to 14.7%. Commonly cited complications included ileus, fecal impaction/bowel obstruction, and cholecystitis. Despite its rarity, one large retrospective review determined the incidence of ACPO after spinal fusion surgery to be 0.04%–0.22%.[16,22]

Risk factors

An abundance of studies analyzed risk factors for the development of POI and GI complications after spine surgery; however, they demonstrated a wide variability in outcomes. While the findings of each study are listed in Table 1, POI risk factors that were found to be significant in at least two studies are summarized in Table 1. POI risk factors that were significant in only one study included anemia, electrolyte/fluid imbalances, weight loss, increased BMI, large change in thoracolumbar kyphosis, total estimated blood loss, intraoperative hypotension, sufentanil (compared to other opioids), intravenous anesthesia (compared to inhaled), use of an “access surgeon,” prone positioning, and posterior lumbar interbody fusion (PLIF), anterior lumbar interbody fusion (ALIF) and open approaches. There were no GI complication risk factors that were found to be significant in more than one study. Only two studies investigated individual GI complications in spine populations: ACPO was associated with male sex, older age, medical comorbidities, electrolyte disorders, and spine deformity diagnoses, while dysphagia was more common in the cervical spine and associated with the anterior approach, history of deep vein thrombosis (DVT), and increased surgery length.[16,37]

Prevention and treatment

Seventeen studies investigated potential prevention techniques for POI in spine surgery patients.[1,17,20,24,25,29,33,38,40,42,45,58,59,60,61,62,68] The main prevention techniques analyzed in the literature were early ambulation, prophylactic medications, early diet restriction, gum-chewing, nonnarcotic pain control, functional score systems as predictive models, and standardized postoperative bowel medication protocols. Very few studies assessed treatment options for POI in spinal surgery populations, specifically. The main treatments that were investigated included nonselective m-opioid antagonists and acetylcholinesterase inhibitors, such as neostigmine. The main recommendations regarding prevention and treatment are summarized in Table 2.

Table 2.

Summary of study findings regarding ileus prevention and treatment techniques in spinal surgery patients

Ileus Prevention Recommendations
Technique	Findings
Early Ambulation	Although one study found no impact on ileus[58], the majority of studies showed early ambulation was associated with decreased ileus rates for single and multilevel procedures[1,56,57]. Of note, the early ambulation group was often voluntary and likely selected for patients with less comorbidities that were feeling well postoperatively, and therefore potentially overestimating the protective effect of early ambulation.
Prophylactic Medications	Prophylactic medications, such as Alvimopan and Methyltrexone, did not impact return to bowel function or decrease ileus rates[32,59,60].
Early Diet Restriction	Inconsistent results with one study showing immediate full diet was associated with increased risk of ileus[29] while another reported it had no impact of ileus development[37]. Of note, patients were not randomly assigned to diet groups and instead were “deemed appropriate for early diet liberalization”.
Gum-chewing	Decreases time to first flatus and first defecation but does not impact ileus development[61]. Gum-chewing could be considered to promote bowel function in patients who are unable to eat in the days following surgery.
Nonnarcotic Pain Control	Overall intraoperative opioid dosing and specific opioids (Remifentanil and Sufentanil) were associated with increased ileus development[17,28,43].
Functional Score Systems as Predictive Model	An Activity Measure for Post-Acute Care (AM-PAC) score of <13 (inability to walk or stand for more than one minute) is associated with ileus development[63]. Functional Score Systems can be used to screen for patients at higher risk of ileus development.
Standardized Post-op Bowel Protocols	Implementing a standardized postoperative bowel medication protocol can lead to low rates of ileus[40]. Of note, the protocol was developed from anecdotal observations from one institution and tested in a small sample size (n=19).
Treatment Recommendations
Technique	Findings
u-opioid receptor antagonists	These medications did not decrease length of stay in ileus patients[23].
Acetylcholinesterase Inhibitors	Treatment with neostigmine lead to prompt colonic decompression and significant reduction in intestinal diameter in small cohort of acute colonic pseudo-obstruction patients[20].

DISCUSSION

POI incidence rates following spine surgery varied significantly in the literature. The study with the lowest POI incidence included cervical spine patients, which is associated with lower rates of ileus, presumably due to decreased abdominal manipulation.[31] The study, which reported the highest rate (35.4%), involved only ALIF patients,[10] an approach that is associated with increased rates of ileus.[11,28,49,50,69] However, a meta-analysis of anterior spine fusion patients found an overall POI incidence of 1.4%,[70] so it is unlikely the approach alone was responsible for the high incidence. The wide variability could be due to billing codes leading to a lack of sensitivity and inconsistency in ileus definitions across the literature. One review found at least five different ileus definitions.[68] Given their rare incidence, no studies reported solely on individual GI complications but instead grouped these together in their analyses. Cumulative GI complication rates ranged from 2.1% to 16.2%, with more severe pathologies such as ACPO having expectedly low incidences of <1%.[16,22]

Investigations into potential POI risk factors yielded mixed results. Seventeen different patient characteristic variables were cited, but only a couple were found to be significant predictors in more than one study (male sex,[9,28,42] electrolyte/fluid imbalance,[23,28] substance abuse,[17,28] hepatobiliary disease,[17,18] and GERD[26,67]). Two meta-analyses have sought to integrate these findings to determine the likely predictors of POI. Reed et al.’s meta-analysis of 297,809 patients found that the only patient characteristic variables associated with POI development were male sex and increased age.[69] A similar meta-analysis by Chang et al. agreed that male sex was a significant predictor, but concluded there were no additional risk factors, including liver disease and electrolyte imbalances.[71]

With regard to surgical variables, the included studies identified several potential risk factors for POI development. Nearly unanimously, increased surgical time,[18,24,25,30,42] increased levels fused,[17,18,28,30,31,38,48,65] and lumbar level surgery[26,31] were significant predictors of ileus development, which was supported by several meta-analyses.[69,71] It is difficult to ascertain whether increased surgery time in itself leads to GI dysmotility or if it simply reflects more complex procedures. Although some studies cited LLIF and PLIF as risk factors, the majority of studies found the anterior approach (ALIF) to be associated with POI development, which has hindered its transition to the outpatient setting.[72] Interestingly, only one of the two meta-analyses found the anterior approach to be associated with increased risk of ileus.[69] Unlike posterior approaches, which require no retraction of abdominal viscera,[49] the anterior approach requires entry through or manipulation of the peritoneal cavity to access the retroperitoneal space.[12,50] Studies that found PLIF to be a risk factor hypothesized that posterior approaches risk distracting the innervation of the posterior peritoneum, which could lead to ileus.[6]

Additional surgical variables that yielded conflicting results included open approach, repositioning, osteotomy, and the use of “access surgeons.” Even though only one included study concluded laparoscopic surgery was associated with shorter duration of ileus,[64] this finding was corroborated by a meta-analysis, which found laparoscopic surgery was associated with decreased risk of ileus compared to open.[69] Although it appears positioning does not impact rates of symptomatic ileus, a series of studies asserted that repositioning from supine/lateral decubitus to prone increases the risk of POI compared to single position approaches. The reduction in ileus is likely due to a combination of increased retraction of the peritoneum, longer operative time, increased blood loss, and increased opioid administration.[53,54] While it is unclear if osteotomies increase POI risk,[38,68] opening wedge osteotomies have higher rates of ileus than closing wedge osteotomies. Perhaps the elongation of the lumbar spine seen in opening wedge osteotomy increases tension on the anterior abdominal organs.[52] Interestingly, two articles[10,73] reported that the use of an “access surgeon” was associated with POI development. One explanation is that access surgeons are utilized more frequently in more complex cases, which are more likely to develop ileus at baseline.

Many experts hypothesize that opioid use contributes to POI, and the high prevalence of ileus following spine surgery is likely attributable to its high pain burden and consequent high opioid use.[19] Although there were mixed results on whether total intraoperative opioid dosing or total 24-hr postoperative opioid dosing is associated with ileus development in some way, and certain opioids (i.e., remifentanil) confer increased risk of POI compared to other intraoperative opioids. Given the lack of consensus, more studies are needed to elucidate this association with respect to type, timing, and cumulative dosing.

Given what is known about risk factors, spine surgeons can take several steps to minimize the occurrence of ileus in high-risk patients. Patients with elevated risk scores should be counseled and receive careful preoperative medical management.[38] Several studies have suggested utilizing a free and minimally invasive derived point scale to stratify patients by POI risk.[17,63,68] An Activity Measure for Post-Acute Care “6-Clicks” score of <13 was found to have 8 times greater odds of developing ileus, and could be used as a screening tool to find patients that would benefit from prophylactic treatment.[63] Given the association between opiate use and ileus development, it is imperative to have discussions with anesthesia providers who directly determine intraoperative dosing to optimally minimize intraoperative opioid use.[17] In addition to anesthesiologists, early consultation with gastroenterologists and general surgeons is recommended to avoid preventable complications.

There were several prevention techniques that showed promise in reducing ileus burden after spine surgery, including early ambulation and gum-chewing. Despite some inconsistency, most studies concluded that early ambulation decreases the risk of ileus. Patients may be unable to ambulate on the day of surgery. In many studies, the early ambulation group was voluntary and likely selected for patients with less comorbidities who were feeling well postoperatively, which potentially overestimates the protective effect of early ambulation.[58] Although its effect on ileus is unclear, ambulation should be encouraged as early and as safely as possible due to an association with decreased LOS, earlier rehab discharge, and lower rates of medical complications.[27,37,33] Although chewing gum has been shown to promote bowel function recovery and reduce POI duration in non-spinal patients[62,74,75], studies investigating spine surgery patients found that gum chewing did not prevent ileus. However, for patients who are unable to eat in the days following surgery, gum chewing could be considered as an adjunctive treatment.

Although restriction of early oral intake after surgery has been cited as a simple prevention strategy,[6] several included studies found that early oral intake is not associated with increased ileus and can actually reduce POI by stimulating bowel motility.[25,42] The delayed diet group had significantly increased levels of fused/decompressed and surgery durations compared to the early diet group, which could explain why the early diet was not associated with increased ileus.[42] Overall, early feeding can be “safe” after certain surgeries, but likely does not reduce POI.[76,77] Despite the selective opioid antagonists Alvimopan and Methylnaltrexone showing consistent GI motility benefits in nonspine surgery patients,[12,76,78,79,80,81] neither of these prophylactic medications was successful in preventing ileus development in spine surgery patients. Other prophylactic GI motility medications include scopolamine, butylbromide, and metoclopramide hydrochloride,[40,76] but neither has been investigated in spine surgery. It seems the best prevention strategy is to optimize postoperative nutrition, ambulate as early as possible, and utilize nonnarcotic pain control strategies if able.[21]

Given the high risk of complications in spine surgery populations, surgeons should have a high suspicion and a low threshold for involving specialists.[2] For simple constipation, physicians can encourage early mobilization, increase oral fluid intake and dietary fiber, and prescribe laxatives and stool softeners.[6] If there is suspicion of ileus, a diagnosis can be made by ruling out mechanical obstruction via single-contrast water-soluble barium enema, CT scan, or colonoscopy.[2,22] Although rare, SMA syndrome and ACPO can mimic ileus and should be considered in the differential.[22,35] Once the diagnosis of ileus has been established, symptoms typically resolve with conservative management, including nothing by mouth (NPO), IV fluid maintenance, electrolyte replacement, laxatives, and adding NG intubation in cases of severe bloating and nausea.[2,6,12,13,17,20,21,22] If conservative treatment fails, physicians can add promotility agents such as neostigmine, metoclopramide, and opiate antagonists.[6,13,21,22,76] Neostigmine is a cholinesterase inhibitor that has been shown to be successful in the treatment of ileus in nonspinal patients, but should be reserved for cases in which bowel ischemia or perforation has been excluded.[6,20,21,22,82] In cases of prolonged ileus refractory to treatment, patients are at high risk for perforation, and colonoscopic decompression is indicated.[20] Percutaneous colostomy and surgical cecostomy are appropriate in symptomatic patients with extreme colonic dilation,[21] and laparotomy with diversion ileostomy is required in the event of bowel perforation.[22] Despite the high prevalence of POI and GI complications, the majority of studies investigating treatment efficacy are not performed on spine surgery populations, and more research is needed to create a set of standardized treatment protocols.[2,45]

This systematic review had several limitations. There was a wide variability in the findings regarding ileus and GI complication rates, which was likely due to the fact that spine surgery is very heterogeneous. In order to maximize the number of included studies investigating prevention and treatment, we chose to expand our study population to include all types of spine surgery, which likely contributed to this variability. Furthermore, there were few studies investigating individual GI complications and management plans, which is likely due to their low rates of occurrence and therefore inadequate sample sizes. Despite POI being a well-documented complication in spine patients, there are few studies looking at the prevention and treatment specifically in spine surgery patients, whereas most of the recommendations stem from studies in colorectal surgery patients.

CONCLUSION

The incidence of POI after spinal surgery is high. Common risk factors for POI were male sex, increased surgical time, increased opioid use intraoperatively, increased number of levels fused, and surgery on the lumbar spine. Early ambulation for prevention and early recognition for treatment is important.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.