Preoperative electroacupuncture versus sham electroacupuncture for the treatment of postoperative ileus after laparoscopic surgery for colorectal cancer in China: a study protocol for a multicentre, randomised, sham-controlled trial.

INTRODUCTION: Postoperative ileus (POI) is a postoperative complication that can cause lingering recovery after colorectal resection and a heavy healthcare system burden. Acupuncture aims to prevent postoperative complications, reduce the duration of POI, help recovery and shorten hospital stays. We hypothesise that preoperative electroacupuncture (EA) can promote POI recovery under the enhanced recovery after surgery protocol after laparoscopic surgery in patients with POI. METHODS AND ANALYSIS: This is a multicentre, randomised, sham-controlled trial. A total of 80 patients will be enrolled and randomly assigned to the EA or sham electroacupuncture (SA) group. The eligible patients will receive EA or SA for one session per day with treatment frequency starting on preoperative day 1 for four consecutive days. The primary outcome is the time to first defecation. The secondary outcomes include the time to first flatus, length of postoperative hospital stay, time to tolerability of semiliquid and solid food, postoperative nausea, vomiting, pain and extent of abdominal distention, time to first ambulation, preoperative anxiety, 30-day readmission rate, the usage of anaesthetics and analgesics during operation, length of postanaesthesia care unit stay. A mechanistic study by single-cell RNA sequencing in which postintervention normal intestinal tissue samples will be collected. The results of this study will provide evidence of the effects of acupuncture on POI and promote good clinical decision to millions of patients globally every year. ETHICS AND DISSEMINATION: This study has been approved by the ethical application of Beijing University of Chinese Medicine (2022BZYLL0401), Beijing Friendship Hospital Affiliated to Capital Medical University(2022-P2-368-02), Cancer Hospital Chinese Academy of Medical Science (23/175-3917), Huanxing Cancer Hospital (2023-002-02). The results will be published in a medical journal. In addition, we plan to present them at scientific conferences. TRIAL REGISTRATION NUMBER: ChiCTR2300077633.

Personalized risk prediction for prolonged ileus after minimally invasive colorectal cancer surgery: in-depth risk factor analysis and model development.

PURPOSE: Despite the increasing preference for minimally invasive surgery for colorectal cancer (CRC), the incidence of prolonged postoperative ileus (PPOI) remains high. Thus, this study aimed to identify risk factors for PPOI in patients with CRC who underwent minimally invasive surgery (MICRS) and to develop a practical nomogram for predicting individual PPOI risk. METHODS: A consecutive series of 2368 patients who underwent MICRS between 2013 and 2023 at two tertiary academic centers were retrospectively studied. Using the data from 1895 patients in the training cohort, a multivariable logistic regression model was employed to select significant variables for the construction of a best-fit nomogram. The nomogram was internally and externally validated. RESULTS: PPOI occurred in 9.5% of patients. Six independent risk factors were identified to construct a nomogram: advanced age (OR 1.055, P = 0.002), male sex (OR 2.914, P = 0.011), age-adjusted Charlson comorbidity index ≥ 6 (OR 2.643, P = 0.025), preoperative sarcopenia (OR 0.857, P = 0.02), preoperative prognostic nutritional index (OR 2.206, P = 0.047), and intraoperative fluid overload (OR 2.227, P = 0.045). The AUCs of the model for predicting PPOI in the training and external validation cohorts were 0.887 and 0.838, respectively. The calibration curves demonstrated excellent consistency between the nomogram-predicted and observed probabilities in both cohorts. Individuals with a total nomogram score of < 197 or ≥ 197 were considered to be at low or high risk for PPOI, respectively. CONCLUSIONS: The integrated nomogram we developed could provide personalized risk prediction of PPOI after MICRS. This quantification enables surgeons to implement personalized prevention strategies, thereby improving patient outcomes.

Comparison of low versus high (standard) intraabdominal pressure during laparoscopic colorectal surgery: systematic review and meta-analysis.

BACKGROUND: To evaluate outcomes of low with high intraabdominal pressure during laparoscopic colorectal resection surgery. METHODS: A systematic search of multiple electronic data sources was conducted, and all studies comparing low with high (standard) intraabdominal pressures were included. Our primary outcomes were post-operative ileus occurrence and return of bowel movement/flatus. The evaluated secondary outcomes included: total operative time, post-operative haemorrhage, anastomotic leak, pneumonia, surgical site infection, overall post-operative complications (categorised by Clavien-Dindo grading), and length of hospital stay. Revman 5.4 was used for data analysis. RESULTS: Six randomised controlled trials (RCTs) and one observational study with a total of 771 patients (370 surgery at low intraabdominal pressure and 401 at high pressures) were included. There was no statistically significant difference in all the measured outcomes; post-operative ileus [OR 0.80; CI (0.42, 1.52), P = 0.50], time-to-pass flatus [OR -4.31; CI (-12.12, 3.50), P = 0.28], total operative time [OR 0.40; CI (-10.19, 11.00), P = 0.94], post-operative haemorrhage [OR 1.51; CI (0.41, 5.58, P = 0.53], anastomotic leak [OR 1.14; CI (0.26, 4.91), P = 0.86], pneumonia [OR 1.15; CI (0.22, 6.09), P = 0.87], SSI [OR 0.69; CI (0.19, 2.47), P = 0.57], overall post-operative complications [OR 0.82; CI (0.52, 1.30), P = 0.40], Clavien-Dindo grade ≥ 3 [OR 1.27; CI (0.59, 2.77), P = 0.54], and length of hospital stay [OR -0.68; CI (-1.61, 0.24), P = 0.15]. CONCLUSION: Low intraabdominal pressure is safe and feasible approach to laparoscopic colorectal resection surgery with non-inferior outcomes to standard or high pressures. More robust and well-powered RCTs are needed to consolidate the potential benefits of low over high pressure intra-abdominal surgery.

Cecal volvulus - a rare cause of acute abdomen with ileus.

In this article, we present case reports of two patients admitted to the University Hospital in Pilsen for acute abdomen due to a disorder of the passage through the gastrointestinal tract (GIT). Both were indicated for surgery. The patients were diagnosed intraoperatively with rarely occurring cecal volvulus (CV). The findings required an ileocecal resection; nevertheless, both patients fully recovered despite the need the resection.

Determining the need for surgery in small bowel obstructions based on clinical, laboratory, and radiological parameters.

OBJECTIVE: Small bowel obstruction (SBO) is a common and important surgical emergency. Our aim in this study is to describe the clinical, laboratory, and computed tomography (CT) findings to facilitate the objective identification of SBO patients in need of operative treatment in this patient population. METHODS: This retrospective study included 340 patients hospitalized due to a preliminary diagnosis of ileus. Retrieved data of patients included age, gender, comorbidities, previous hospitalization due to ileus, surgical history, physical examination findings, complete blood count and biochemistry test results, and CT findings at admission. RESULTS: The study included 180 (52.9%) male and 160 (47.1%) female patients. Treatment was conservative in 216 patients and surgery in 124 patients. Of the patients included in the study, 36.4% needed surgery. Of the female patients, 38.90% received conservative treatment and 61.30% underwent surgery. Adhesions were the most common cause of obstruction in operated patients (43.50%). CONCLUSION: We have found that female gender, vomiting, guarding, rebound, C-reactive protein levels above 75 mg/L, increased bowel diameter, and a transition zone on CT images indicate a strong need for surgery, but a history of previous hospitalization for ileus may show that surgery may not be the best option.

OBJETIVO: Describir los hallazgos clínicos, de laboratorio y de tomografía computarizada (TC) para facilitar la identificación objetiva de los pacientes con obstrucción del intestino delgado que necesitan tratamiento quirúrgico. MÉTODO: Este estudio incluyó 340 pacientes. Los datos obtenidos fueron edad, sexo, comorbilidad, hospitalización previa debida a íleo, historia quirúrgica, hallazgos de la exploración física, hemograma completo y resultados de las pruebas bioquímicas, y hallazgos de la TC al ingreso. RESULTADOS: El estudio incluyó 180 (52.9%) varones y 160 (47.1%) mujeres. El tratamiento fue conservador en 216 pacientes y quirúrgico en 124 pacientes. De los pacientes incluidos en el estudio, el 36.4% necesitaron cirugía. De las mujeres, el 38.90% recibieron tratamiento conservador y el 61.30% se sometieron a cirugía. CONCLUSIONES: Encontramos que el sexo femenino, los vómitos, la guardia, el rebote, los niveles de proteína C reactiva superiores a 75 mg/l, el aumento del diámetro intestinal y una zona de transición en las imágenes de TC indican una fuerte necesidad de cirugía.

Postoperative Ileus Murine Model.

Most patients experience postoperative ileus (POI) after surgery, which is associated with increased morbidity, mortality, and hospitalization time. POI is a consequence of mechanical damage during surgery, resulting in disruption of motility in the gastrointestinal tract. The mechanisms of POI are related to aberrant neuronal sensitivity, impaired epithelial barrier function, and increased local inflammation. However, the details remain enigmatic. Therefore, experimental murine models are crucial for elucidating the pathophysiology and mechanism of POI injury and for the development of novel therapies. Here, we introduce a murine model of POI generated via intestinal manipulation (IM) that is similar to clinical surgery; this is achieved by mechanical damage to the small intestine by massaging the abdomen 1-3 times with a cotton swab. IM delayed gastrointestinal transit 24 h after surgery, as assessed by FITC-dextran gavage and fluorescence detection of the segmental digestive tract. Moreover, tissue swelling of the submucosa and immune cell infiltration were investigated by hematoxylin and eosin staining and flow cytometry. Proper pressure of the IM and a hyperemic effect on the intestine are critical for the procedure. This murine model of POI can be utilized to study the mechanisms of intestinal damage and recovery after abdominal surgery.

Short-term outcome of intracorporeal ileocolonic anastomosis in patients with visceral obesity.

The primary objective of this study was to compare short-term outcomes between Intracorporeal ileocolic anastomosis (IIA) and extracorporeal ileocolic anastomosis (EIA) after laparoscopic right hemicolectomy in patients with visceral obesity. The secondary objective was to identify risk factors associated with prolonged postoperative ileus (PPOI) after laparoscopic right hemicolectomy. This single-center retrospective study analyzed visceral obesity patients who underwent laparoscopic right hemicolectomy for primary bowel cancer between January 2020 and June 2023. Patients were categorized into IIA and EIA groups based on the type of anastomosis, and a 1:1 propensity score-matched analysis was performed. A total of 129 patients were initially included in this study, with 45 patients in each group following propensity score matching. The IIA group had significantly longer anastomosis times (p < 0.001), shorter incision length (p < 0.001), and shorter length of stay (p = 0.003) than the EIA group. Meanwhile, the IIA group showed a shorter time to first flatus (p = 0.044) and quicker tolerance of a solid diet (p = 0.030). On multivariate analysis, postoperative use of opioid analgesics is an independent risk factor for PPOI (OR: 3.590 95% CI 1.033-12.477, p = 0.044), while IIA is an independent protective factor (OR: 0.195 95% CI 0.045-0.843, p = 0.029). IIA remains a safe and feasible option for visceral obesity patients. It is also associated with a quicker recovery of bowel function and shorter length of stay when compared to EIA. Additionally, IIA is an independent protective factor for PPOI.

Bouveret Syndrome: A Curious Simultaneous Presentation of Two Cases: Comparison of Clinical Observations and Surgical Management.

Gallstone ileus is an uncommon occurrence and accounts for about 0.3-0.5% of complications of cholelithiasis in elderly patients. Bouveret syndrome is an uncommon medical condition resulting from the blockage of the duodenal bulb by a stone, which consequently obstructs the outlet of the stomach. Until now, a comparison of two different presentations of Bouveret syndrome has not been published in the literature due to the rarity of this pathology. The curious simultaneous occurrence of the two cases discussed here made it possible for us to compare the different diagnostic and therapeutic pathways. In fact, both cases differ not only in their presenting symptoms, but also in the management adopted by the same surgical team.

An outline of the management and prevention of postoperative ileus: A review.

Postoperative ileus (POI) is a prevalent surgical complication, which results in prolonged hospitalization, patient distress, and substantial economic burden. The literature aims to present a brief outline of interventions for preventing and treating POI post-surgery. Data from 2014 to 2023 were gathered from reputable sources like PubMed, PubMed Central, Google Scholar, Research Gate, and Science Direct. Inclusion criteria focused on studies exploring innovative treatments and prevention strategies for POI, using keywords such as novel POI treatments, non-pharmacological prevention, POI incidence rates, POI management, and risk factors. The findings revealed that integration of preventive measures such as coffee consumption, chewing gum, probiotics, and use of dikenchuto within enhanced recovery programs has significantly reduced both the frequency and duration of POI, without any adverse effects, with minimally invasive surgical approaches showing promise as an additional preventive strategy. While treatment options such as alvimopan, NSAIDs, and acupuncture have demonstrated efficacy, the use of lidocaine has raised concerns due to associated adverse effects. The ongoing exploration of novel therapeutic strategies such as targeting the mast cells, vagal nerve stimulation and tight junction protein, and prokinetic-mediated instigation of the cholinergic anti-inflammatory trail not only holds promise for enhanced treatment but also deepens the understanding of intricate cellular and molecular pathways underlying POI. POI presents a complex challenge in various surgical specialties, necessitating a multifaceted management approach. The integration of preventive and treatment measures within enhanced recovery programs has significantly reduced POI frequency and duration.

Enhanced recovery programs following adhesive small bowel obstruction surgery are feasible and reduce the rate of postoperative ileus: a preliminary study.

PURPOSE: The recovery of gastrointestinal function and postoperative ileus are the leading goals for clinicians following surgery for adhesive small bowel obstruction. While enhanced recovery programs may improve recovery, their feasibility in emergency surgery has not yet been proven. We sought to assess the incidence of postoperative ileus in patients following surgery for ASBO and the feasibility of enhanced recovery programs, including their benefits in the recovery of gastrointestinal functions and reducing the length of hospitalization. METHODS: This prospective study includes the first 50 patients surgically treated for ASBO between June 2021 and November 2022. Their surgery was performed either as an emergency procedure or after a short course of medical treatment. The main aim was to compare the observed rate of postoperative ileus with a theoretical rate, set at 40%. The study protocol was registered in clinicaltrials.gov under the number NCT04929275. RESULTS: Among the 50 patients included in this study, it reported postoperative ileus in 16%, which is significantly lower than the hypothetical rate of 40% (p = 0.0004). The median compliance with enhanced recovery programs was 75% (95%CI: 70.1-79.9). The lowest item observed was the TAP block (26%) and the highest observed items were preoperative counselling and compliance with analgesic protocols (100%). The overall morbidity was 26.5%, but severe morbidity (Dindo-Clavien > 3) was observed in only 3 patients (6%). Severe morbidity was not related with the ERP. CONCLUSION: Enhanced recovery programs are feasible and safe in adhesive small bowel obstruction surgery patients and could improve the recovery of gastrointestinal functions. CLINICAL TRIAL REGISTRY: NCT04929275. WHAT DOES THE STUDY CONTRIBUTE TO THE FIELD?: Perioperative management of adhesive small bowel obstruction (ASBO) surgery needs to be improved in order to reduce morbidity. Enhanced recovery programs (ERP) are both feasible and safe following urgent surgery for ASBO. ERPs may improve the recovery of gastrointestinal (GI) functions.

Testing Machine Learning Models to Predict Postoperative Ileus after Colorectal Surgery.

Background: Postoperative ileus (POI) is a common complication after colorectal surgery, leading to increased hospital stay and costs. This study aimed to explore patient comorbidities that contribute to the development of POI in the colorectal surgical population and compare machine learning (ML) model accuracy to existing risk instruments. Study Design: In a retrospective study, data were collected on 316 adult patients who underwent colorectal surgery from January 2020 to December 2021. The study excluded patients undergoing multi-visceral resections, re-operations, or combined primary and metastatic resections. Patients lacking follow-up within 90 days after surgery were also excluded. Eight different ML models were trained and cross-validated using 29 patient comorbidities and four comorbidity risk indices (ASA Status, NSQIP, CCI, and ECI). Results: The study found that 6.33% of patients experienced POI. Age, BMI, gender, kidney disease, anemia, arrhythmia, rheumatoid arthritis, and NSQIP score were identified as significant predictors of POI. The ML models with the greatest accuracy were AdaBoost tuned with grid search (94.2%) and XG Boost tuned with grid search (85.2%). Conclusions: This study suggests that ML models can predict the risk of POI with high accuracy and may offer a new frontier in early detection and intervention for postoperative outcome optimization. ML models can greatly improve the prediction and prevention of POI in colorectal surgery patients, which can lead to improved patient outcomes and reduced healthcare costs. Further research is required to validate and assess the replicability of these results.

[Small bowel obstruction with an unusual background]. / Egy szokatlan hátteru vékonybél ileus.

Bevezetés: Kompressziós vékonybél ileus esetét ismertetjük, amelyet a bélfodor nem gyakori, inflammatorikus természetu betegsége, mesenterialis panniculitis idézett elo. A magyar szakirodalomban ilyen közléssel nem találkoztunk. Esetismertetés: A 91 éves férfi akut hasi panaszokkal került kórházba. A vizsgálatokkal vékonybél ileus derült ki. Ennek hátterében mutétkor malignitásra gyanús, bélfodri multinodularis elváltozást fedtünk föl. A biopsziából mesenterialis panniculitist diagnosztizáltunk. A ritka, több nyitott kérdéssel terhelt entitást mutatjuk be az irodalom és a saját észleleteink tükrében. Következtetések: Számos differenciáldiagnosztikai eshetoség figyelembevételével a kórkép szövettanilag igazolható. A diagnózis felállítása után a további teendoket az egyéb leletek és az adott klinikai kontextus gondos elemzése fogja meghatározni.

The "Tumbling Gallstone Sign" of Obstructive Gallstone Ileus.

The "tumbling gallstone sign" is a diagnostic imaging finding described on radiologic examinations of the abdomen, in patients with cholelithiasis associated with intermittent episodes of gallstone obstructive ileus.  Best seen on serial radiographs or CT studies of the abdomen, this sign indicates a sudden change in position of the gallstone(s) within the intestinal lumen from the upper segments of the bowel to the lower segments of the bowel, causing transient mechanical bowel obstruction.  The tumbling gallstone sign has been likened to that of the classic childrens' tumbling tower balancing game.  On repeat CT scans, the dislodged gallstone(s) may be seen proceeding distally and impact in the ileum at a level lower than that seen on the previous CT scans, analogous to the tumbling gallstone sign.

Pyridostigmine to Reduce the duration of postoperative Ileus after Colorectal surgery (PyRICo-RCT): randomized clinical trial.

BACKGROUND: Postoperative ileus, driven by the cholinergic anti-inflammatory pathway, is the most common complication in patients undergoing colorectal surgery. By inhibiting acetylcholinesterase, pyridostigmine can potentially modulate the cholinergic anti-inflammatory pathway and accelerate gastrointestinal recovery. This study aimed to assess the efficacy of pyridostigmine in improving gastrointestinal recovery after colorectal surgery. METHODS: This double-blinded RCT enrolled adult patients undergoing elective colorectal surgery at two hospitals in South Australia. Patients were randomized to 60 mg oral pyridostigmine or placebo twice daily starting 6 h after surgery until the first passage of stool. The primary outcome was GI-2, a validated composite measure of time to first stool and tolerance of oral diet. Secondary outcomes included incidence of postoperative ileus (defined as GI-2 greater than 4 days), duration of hospital stay, and 30-day complications, evaluated by intention-to-treat univariate analysis. RESULTS: Of 130 patients recruited (mean(s.d.) age 58.4(16.4) years; 73 men, 56%), 65 were allocated to each arm. The median GI-2 was 1 day shorter with pyridostigmine compared with placebo (2 (i.q.r. 1-3) versus 3 (2-4) days; P = 0.015). However, there were no significant differences in postoperative ileus (17.2 versus 21.5%; P = 0.532) or duration of hospital stay (median 5 (i.q.r. 4-8.75) versus 5 (4-7.5) days; P = 0.921). Similarly, there were no significant differences in overall complications, anastomotic leak, cardiac complications, or patient-reported side effects. CONCLUSION: Pyridostigmine resulted in a quicker return of GI-2 and was well tolerated. Larger multicentre studies are required to determine the optimal dosing and evaluate the impact of pyridostigmine in different surgical settings. Registration number: ACTRN12621000530820 (https://anzctr.org.au).

[Gallstone ileus as a cause of mechanical intestinal obstruction: a case report]. / íleo biliar como causa de obstrucción intestinal mecánica: reporte de un caso.

Biliary ileus is a mechanical intestinal obstruction characterized by symptoms such as abdominal pain, jaundice and fever. The treatment of choice in these cases is associated with a surgical approach according to the clinical condition of the patient. It is important to study this pathology since its timely diagnosis and treatment are essential to avoid serious complications associated with high morbidity and mortality. This article describes a case related to biliary ileus.

Effects of transcutaneous electrical nerve stimulation on recovery of gastrointestinal motility after laparotomy: A randomized controlled trial.

INTRODUCTION: Postoperative Ileus (POI) negatively impacts patient outcomes and increases healthcare costs. Transcutaneous electrical nerve stimulation (TENS) has been found to improve gastrointestinal (GI) motility following abdominal surgery. However, its effectiveness in this context is not well-established. This study was designed to evaluate the role of TENS on the recovery of GI motility after exploratory laparotomy. METHODS: Patients undergoing exploratory laparotomy were randomized in a 1:1 ratio into control (standard treatment alone) and experimental (standard treatment + TENS) arms. TENS was terminated after 6 days or after the passage of stool or stoma movement. The primary outcome was time for the first passage of stool/functioning stoma. Non-passage of stool or nonfunctioning stoma beyond 6 days was labeled as prolonged POI. Patients were monitored until discharge. RESULTS: Median (interquartile range) time to first passage of stool/functioning stoma was 82.6 (49-115) hours in the standard treatment group and 50 (22-70.6) hours in the TENS group [p < 0.001]. Prolonged POI was noted in 11 patients in the standard treatment group (35.5%) and one in the TENS group (3.2%) [p = 0.003]. Postoperative hospital stay was similar in the two groups. CONCLUSION: TENS resulted in early recovery of GI motility by shortening the duration of POI without any improvement in postoperative hospital stay. TRIAL REGISTRATION NUMBER: CTRI/2021/10/037054.

Meckel's diverticulum is a rare cause of mechanical ileus in adults.

Meckel's diverticulum is the most common congenital gastrointestinal defect with a prevalence of 2%. It is mostly asymptomatic and it rarely causes acute abdomen in adults. In this case report, a 28-year-old male with no previous abdominal surgery presented with clinical symptoms of small bowel obstruction. Surgery revealed a Meckel's diverticulum adherent to the abdominal wall, causing internal herniation with small bowel obstruction. The diverticulum was openly resected and no post-operative complications occurred. Laparoscopy seems safe, and surgical removal of the symptomatic Meckel's diverticulum is recommended.

The impact of low pressure pneumoperitoneum in robotic assisted radical prostatectomy II: a prospective, randomized, double blinded trial.

OBJECTIVE: To analyze postoperative ileus rates and postoperative complications between the different pneumoperitoneum settings. The secondary objective was to evaluate narcotic use and intraoperative blood loss between the different pneumoperitoneum settings. METHODS: A prospective, randomized, double blinded study was conducted at pneumoperitoneum pressures of either 12 mmHg or 15 mmHg for patients undergoing robotic assisted radical prostatectomy with bilateral pelvic lymph node dissection by a single high volume surgeon. RESULTS: The risk of ileus in the 12 mmHg group was 1.9% (2/105) compared to 3.2% (3/93) in the 15 mmHg group (OR 0.58, 95%CI 0.1-3.6). There was no difference in the risk of any complication with a complication rate of 4.8% (5/105) in the 12 mmHg arm compared to 4.3% (4/93) in the 15 mmHg arm (OR 1.1, 95% CI 0.3 - 4.3). CONCLUSION: Pneumoperitoneum pressure setting of 12 mmHg has no significant difference to 15 mmHg in the rate of postoperative complications, narcotic use, and intraoperative bleeding. Additional research is warranted to understand the optimal.

Risk prediction algorithms for prolonged postoperative ileus: A systematic review.

AIM: Prolonged postoperative ileus (PPOI) is common and is associated with a significant healthcare burden. Previous studies have attempted to predict PPOI clinically using risk prediction algorithms. The aim of this work was to systematically review and compare risk prediction algorithms for PPOI following colorectal surgery. METHOD: A systematic literature search was conducted using MEDLINE, Embase, Web of Science and CINAHL Plus. Studies that developed and/or validated a risk prediction algorithm for PPOI in adults following colorectal surgery were included. Data were collected on study design, population and operative characteristics, the definition of PPOI used and risk prediction algorithm design and performance. Quality appraisal was assessed using the PROBAST tool. RESULTS: Eleven studies with 87 549 participants were included in our review. Most were retrospective, single-centre analyses (6/11, 55%) and rates of PPOI varied from 10% to 28%. The most commonly used variables were sex (8/11, 73%), age (6/11, 55%) and surgical approach (5/11, 45%). Area under the curve ranged from 0.68-0.78, and only three models were validated. However, there was significant variation in the definition of PPOI used. No study reported sensitivity, specificity or positive/negative predictive values. CONCLUSION: Currently available risk prediction algorithms for PPOI appear to discriminate moderately well, although there is a lack of validation data. Future studies should aim to use a standardized definition of PPOI, comprehensively report model performance and validate their findings using internal and external methodologies.