This study sought to evaluate and better understand the diagnostic practices surrounding suction and incisional rectal biopsy for diagnosis of HSCR at our institution and to specifically examine adequacy of biopsy related to type of rectal biopsy performed and its relationship to the age of the patient. While in practice, proceduralists tend to move towards open incisional biopsy in older patient populations, there is no consensus or best practice guideline for determining the specific age of this transition.
Previous investigators have examined the relationship of age and suction vs incisional rectal biopsy. Croffie et al. performed a prospective study in children over 1 year of age, aiming to determine at what age suction rectal biopsy (versus incisional biopsy) was more likely to be inadequate due to insufficient submucosal tissue to detect ganglion cells.[11] However in this study, all biopsies were performed under general anesthesia, which differs from our institutional practice of performing suction rectal biopsies under 6 months old without sedation in clinic. Additionally, while the incisional biopsy was superior to suction biopsy at all ages in terms of providing an adequate sample size, in the 1-3-year-old patient population there was no significant difference between the incisional and suction biopsy with regard to adequacy of the sample. Muise et al. also evaluated suction vs incisional rectal biopsy and the relationship with age of the patient.[12] They conducted a retrospective comparison of suction and full-thickness rectal biopsy in 47 infants and children undergoing work up for HSCR. The results were compared between patients greater vs less than 12 months of age. The authors did not identify a significant difference in adequacy based on technique or age, however, all of the older patients had their biopsies performed in the operating room, regardless of the type of biopsy performed. In contrast, our institution generally uses a 6-month age to move towards open incisional rectal biopsy and again, suction rectal biopsies are performed without sedation or general anesthesia.
In our study, we sought to examine whether our current practice of recommending incisional biopsies for older patients, due to the assumption that a suction biopsy may be more likely to be inadequate in older patients, is warranted. Our review included biopsy results for 225 patients, with an even distribution between incisional and suction rectal biopsies. The patients in the incisional group were, on average, older at time of biopsy, likely reflecting a pre-existing trend at our center towards performing incisional biopsies on older patients. Our study found a substantially higher inadequacy rate in the suction biopsy group compared to the incisional cohort among older patients, those over 6 months of age. Among the suction biopsies alone, inadequacy rates were significantly higher at both the biopsy and procedure level for those patients 6 months and older.
Potential explanations for the increase in inadequacy seen in suction biopsies over 6 months include patient cooperation, as suction biopsies are performed unsedated at our institution and older, larger infants are less likely to comply with the procedure. The findings in our review may also be explained by the decreased density of ganglion cells in the submucosa that is seen with age. Furthermore, older children, especially those with chronic constipation, likely have a larger rectal vault, thus obtaining an adequate mucosal sample can be more difficult when performing a suction biopsy. This may necessitate larger biopsies in older children to achieve an equivalent adequate result.[9] [10] [11]
In the present study we demonstrated that taking more than one biopsy (multiple passes) during a suction rectal biopsy procedure also greatly decreased the chances of an inadequate biopsy. The addition of calretinin staining as a means of reducing inadequacy rates is also important to note, as none of the suction biopsies where calretinin staining was performed were inadequate compared to 14% of those without calretinin staining. However, most suction biopsies were deliberately selected from an era (prior to 2009), which pre-dated both the simultaneous introduction of calretinin staining at our institution and shift towards incisional biopsies for patients > 6 months of age. Therefore, it is difficult to draw any firm conclusions about the effect of calretinin immunohistochemistry on reducing inadequacy rates for suction biopsies from older patients. Additionally, the reason for inadequacy in almost half of the suction biopsies was that the sample was performed at too distal a location in the anal canal and captured anal mucosa. In these cases, calretinin would not have provided additional value. However this finding further supports the notion that more than one level of suction biopsy would be of benefit to decrease the chance of inadequacy.
Practice at our institution has shifted over time to rectal suction biopsies being universally performed by a surgical provider. As seen in our results, higher inadequacy rates were noted among gastroenterologists performing suction biopsies. This may be explained by an older median patient age in the group of patients who had biopsies performed by gastroenterologists. Gastroenterologists were also less likely to obtain multiple biopsies during the procedure when compared to surgeons. This is consistent with results reported by Stewart et al., who demonstrated children undergoing a suction biopsy by a pediatric surgeon were significantly younger when compared to the age of the patients biopsied by a gastroenterologist and surgeons typically yielded a higher biopsy adequacy rate.[13] In our current practice, the suction rectal biopsy technique is performed uniformly by general surgeons with a specialized rectal biopsy instrument. Biopsies are also always taken at three levels and utilizes a specific cartridge that allows for measurement of the biopsy site within the anal canal.
For incisional biopsies, inadequacy was low for both the < 6-month age-group and for the older cohort. Inadequacy was more frequent in the “partial full-thickness” group (containing only submucosa or submucosa plus muscularis interna) compared to the “true full-thickness” group. However, the numbers were relatively small and therefore these results may not be broadly generalizable. Our analysis only focused on evaluation for HSCR and the potential additional diagnostic value (e.g., exclusion of non-Hirschsprung neuromuscular pathology) offered by a true full-thickness versus partial full-thickness biopsy was not addressed.
Limitations of the study include the retrospective design and therefore, the reliance on documentation in the medical record. While the specific technique described previously for suction rectal biopsy is generally accepted at our institution, due to the retrospective nature we are unable to determine if the suction biopsies were performed with the correct method. However, the goal of this study was to assess outcomes at our institution and to determine if these results support current diagnostic practices, particularly recommending incisional biopsies in older patients.
A secondary limitation lies with the patient populations identified spanning slightly different time periods, 1/2003-12/2008 for suction rectal biopsy patients and 1/2000-12/2018 for incisional rectal biopsy patients. The suction rectal biopsy patients were intentionally limited to the pre-2009 era after which our institution shifted to surgeons only performing these biopsies. Additional changes at this time at our institution included three biopsies performed per suction rectal biopsy procedure, routine calretinin staining, and a shift to primarily full thickness rectal biopsies after 6 months of age. As our aim was to investigate the role of many of these variables independently, we elected to evaluate suction biopsies prior to the establishment of these standards. Incisional biopsies both pre- and post-2009 were performed by surgeons from a single site, and therefore, extending the inclusion period forward through 2018 allowed us to increase the number of incisional biopsies without compromising the investigation. In order to address the limitation of retrospective data collection, a single pathologist re-reviewed all the inadequate biopsies to mitigate any potential confounding that could have resulted from pathologic analysis being performed by multiple pathologists. While our initial sample size was moderately large, inadequacy rates, especially for the incisional biopsies were low, making it difficult to draw firm conclusions. It is worth noting that most of our suction biopsies came from one institution (a tertiary pediatric care center) with high surgical and pathology expertise relating to HSCR. It is likely that experience at other centers and standards for number of biopsies, number of histologic sections, use of ancillary studies and diagnostic threshold for inadequacy may differ, which may reduce the generalizability of some of our results and conclusions.
In conclusion, adequacy of rectal biopsies for the diagnosis of HSCR was influenced by the age of the patient, the service performing the biopsy, and the type of biopsy (incisional vs. suction). The rate of inadequate rectal biopsies was low with incisional biopsies in all age groups. At our institution, incisional rectal biopsies were superior to rectal suction biopsies in children greater than 6 months of age. Prospective longitudinal studies with a larger sample size are needed to further validate these findings.