In colon and rectal surgery, the overall intraoperative conversion rates is reported between 2% and 30% [1–6] depending on the pathology, planned procedure, and date of publication. Recently published meta-analysis data suggests that the conversion rate of single-incision laparoscopic surgery (SILS) to laparotomy is as low as 0.9%, while conversion to multi-port laparoscopy surgery (MPLS) is 13.3% [7]. Though the individual reasons for conversion to multi-port, hand-assisted laparoscopic surgery (HALS) or laparotomy will vary, they generally revolve around patient safety directly through iatrogenic injury and indirectly through failure to progress in the dissection. Patient selection, an efficient operating suite, and a mentally prepared operator are the best tools for maximizing the rate of successful SILS.

There are numerous intraoperative complications that might force an operator to consider conversion to multi-port, hand assist, or laparotomy . This section will provide pearls for mitigating possible complications before and after they have occurred [8–10]. In the particular case of hemorrhage or other complications that might alter patient hemodynamics, it is advisable to communicate pertinent information to the anesthesiologist early and often so they may better tailor their resuscitation.

With SILS or any other operative approach, set up your operating room to help you succeed. Operating room setup is addressed before the patient enters the room. Ensure that the correct sized instruments, clip applier, harmonic, stapler, suction catheter, and camera, are available and that the correct length, bariatric vs. normal, instruments are available. Regardless of the perceived complexity, ensure the tools needed in case of conversion are available in the room.

Placing the Mayo stand at the base of the bed can facilitate simple instrument swapping without the surgeon needing to avert their eyes from the screen. This orientation allows electrical devices and grounding cords to be gathered in a single location at the base of the bed preventing cumbersome nests or cords that can potentially entangle the surgical staff.

Having multiple sizes and angles for the camera is suggested for SILS, including a flexible endoscopy tip capable of multiple degrees of freedom. A right-angle light cord is especially useful for SILS as it mitigates external collisions. Finally, ensuring that the camera and light cord have sufficient laxity to traverse all available laparoscopic entry points will facilitate ease of conversion to MPLS [8, 9].

Single-incision laparoscopy and robotics have the distinct advantage over multi-port laparoscopy in that a modest continuous incision is used for placement of the operating port. This allows abdominal entry under direct vision through a generous skin incision. When SILS must be converted to MPLS , additional ports can be placed under direct vision or palpation. Similarly if conversion to HALS or laparotomy is necessary, the incision can be extended to facilitate the existing single-incision port.

Early laparoscopy utilized oxygen as a medium of insufflation; however, this practice was abandoned with the realization that electrical devices in a high oxygen environment were prone to explosions. Carbon dioxide (CO2) insufflation proved more stable with the added benefit that healthy patients can easily metabolize CO2. Insufflation pressure can be modulated based on desired visibility and patient hemodynamics, and if the patient is unable to tolerate pneumoperitoneum, the operator should consider converting to laparotomy or aborting the procedure for further preoperative optimization.

Interesting complications of pneumoperitoneum revolve around inadequate metabolism of CO2 and extra-abdominal accumulation of CO2. Capnothorax is a phenomenon caused by insufflation of the thorax with CO2, directly (thoracoscopy) or indirectly through microscopic (physiologic) or macroscopic (hiatal hernia, iatrogenic diaphragm injury) defects in the diaphragm, and can ultimately create tension physiology and hemodynamic instability [11]. Physiologically, animal testing has shown that the hemodynamic compromise stems from increased thoracic pressure causing decreased venous return and a hyperdynamic state from hypercarbia [12]. The increased cardiac output from hypercarbia is unable to overcome the decreased preload and cardiovascular collapse ensues. Intraoperatively, this can be confirmed by visualizing the hemidiaphragms being displaced caudally in addition to decreased breath sounds. Management of the clinically significant capnothorax—a drop in systolic pressure between 15 and 35 mmHg, increased airway pressures, PaCO2 greater than 50 mmHg, or SpO2 less than 95%—requires immediate surgical evacuation by means of thoracic vent and evacuation of pneumoperitoneum [11, 13–15]. Following hemodynamic stabilization, insufflation can be attempted, but subsequent failure should be treated with conversion to open surgery. Conversely, capnothorax without hemodynamic compromise can be managed with observation and usually resolves shortly into the postoperative period [15, 16].

Drawing from the conclusions of the CLASSIC trial , the higher rate of conversion (16–34%) in early MPLS was due to excessive tumor fixity, uncertainty of tumor clearance or anatomy, surgeon experience, and obesity [5, 17]. These five factors converge on a single concept, a failure to progress the dissection in a safe manner. Studies have shown that while minimally invasive surgery (MIS) is superior to open surgery, there are diminishing returns in patient outcomes as operative time surpasses 180 min. Specifically, delay in discharge and increased infectious cardiopulmonary and cerebrovascular complications become comparable [18, 19]. Thankfully, it does not seem that overall mortality, incidence of intraoperative complications, or rate of reoperation is significantly impacted by prolonged operative time [19]. In fact, cases that begin with MIS and end with open surgery still enjoy a fraction of the benefits of the MIS approach especially when conversion is performed earlier [20]. Furthermore, conversion for non-metastatic disease was associated with a similar rate of positive surgical margins, a slightly improved nodal yield, and a shorter hospital stay with similar 30-day mortality compared to open colectomy [21].

The causes of failure in progression can be extrapolated from the conclusions in the CLASSIC trial : inflammation, unclear or obstructive anatomy, and operator experience. With the rising prevalence of obesity in America (BMI >25) [22], analyzing the effects of BMI on surgical outcomes has been popular. The visceral adiposity and larger abdominal wall as well as the caudal migration of the umbilicus have added complexity to all MIS procedures. Multiple studies have shown direct links to complications related to obesity including superficial, deep, and organ space infections, longer operative times, and incisional hernia formation [1, 23, 24] as well as conversion from MIS to laparotomy [18, 25, 26]. While robotic surgery seems to be more insulated from obesity compared to laparoscopy [1, 26], it still suffers from infectious and hernia complications as BMI increases [18, 25] and is still thwarted by dense adhesions as much as laparoscopy [1].

Advanced tumors, prior radiation, and pathology resulting from inflammatory conditions like diverticulitis and inflammatory bowel disease add technical challenges, with increased anatomic fixity [2, 3]. However, multiple large meta-analyses have shown no difference in margin clearance or overall short-term mortality with SILS compared to MPLS [27]. Tumor size and adhesions from prior surgery seemed to have the same general effect on SILS and MPLS in their conversion rates to laparotomy; however, tumor size and adhesions do not have a significant impact on conversion from SILS to MPLS [27]. Left-sided SILS was reported more demanding compared to right-sided SILS with longer operative times due in part to difficulty in mobilizing the splenic flexure [28]. Pertaining to the rectum, successful total mesorectal excision was achievable with equal operative times and complication rates in SILS vs. MPLS; however, as tumors drifted toward the anal verge, the necessity of additional ports increased to maintain low complication rates [29, 30].

SILS for diverticular disease has reported conversion rates between 4% and 7%; new data suggests a possibly even lower conversion threshold of less than 1% for elective resection in high-volume centers [26, 28, 31, 32]. Data is not as robust for Crohn’s, but as expected for complex inflammatory bowel disease, SILS is feasible but has a higher conversion rate, between 5% and 15% [33–35]. At the current time, a large dataset on SILS for chronic ulcerative colitis is lacking, but smaller series do not report appreciable conversions rates for total abdominal colectomy and restorative proctocolectomy with ileal pouch-anal anastomosis [36–38].

HALS can help conversion from SILS while maintaining MIS benefits. HALS, first released in the mid-1990s, utilizes a minilaparotomy incision (3–6 cm) with a self-sealing retractor port which allows the surgeon to use their hand intracorporeally without sacrificing insufflation. Over the past two decades, HALS has gained popularity secondary to its decreased operative times compared to strict laparoscopy, restoration of direct tactile sensation, and non-inferiority of oncologic outcomes [39, 40]. It also boasts the benefits of laparoscopy with reduced blood loss, decreased postoperative pain, earlier return of bowel function, and shorter hospital stay [41, 42]. HALS is a very effective tool to aid the less experienced laparoscopist through their learning curve with strict laparoscopy as well as being a step between SILS, MPLS , and laparotomy. Conveniently, for most laparoscopic colectomy procedures, a minilaparotomy incision is required for specimen extraction, extracorporeal anastomosis, or stoma maturation allowing utilization of the hand-assist port without an additional incision. The following are pearls related to HALS [8, 43]: