Unusual Presentation of a Sigmoid Mass with Chicken Bone Impaction in the Setting of Metastatic Lung Cancer

Background Ingestion of foreign bodies can cause various gastrointestinal tract complications including abscess formation, bowel obstruction, fistulae, haemorrhage, and perforation. While these foreign body-related complications can occur in normal bowel, diseased bowel from inflammation, strictures, or malignancy can cause diagnostic difficulties. Endoscopy is useful in visualising the bowel from within, providing views of the mucosa and malignancies arising from here, but its ability in diagnosing extramural malignancies arising beyond or external to the mucosa of the bowel as in the case of metastatic extramural disease can be limited. Case Summary We present the case of a 60-year-old female with an impacted chicken bone in the sigmoid colon with formation of a sigmoid mass, on a background of metastatic lung cancer. On initial diagnosis of her lung cancer, there was mild Positron Emission Tomography (PET) avidity in the sigmoid colon which had been evaluated earlier in the year with a colonoscopy with findings of diverticular disease. Subsequent computed tomography (CT) scans demonstrated thickening of the sigmoid colon with a structure consistent with a foreign body distal to this colonic thickening. A repeat PET scan revealed an intensely fluorodeoxyglucose (FDG) avid mass in the sigmoid colon which was thought to be inflammatory. She was admitted for a flexible sigmoidoscopy and removal of the foreign body which was an impacted chicken bone. She had a fall and suffered a fractured hip. During her admission for her hip fracture, she had an exacerbation of her abdominal pain. She developed a large bowel obstruction, requiring laparotomy and Hartmann's procedure to resect the sigmoid mass. Histopathology confirmed metastatic lung cancer to the sigmoid colon. Conclusion This unusual presentation highlights the challenges of diagnosing ingested foreign bodies in patients with metastatic disease.


Introduction
Around 20% of ingested foreign bodies fail to pass through the gastrointestinal tract [1]. These can result in complications such as abscess formation, bowel obstruction, fistulae, haemorrhage, and perforation [2]. These complications can present in a variety of different clinical scenarios. The purpose of this case report was to highlight a scenario in which an ingested foreign body may present, and to outline the challenges of reaching the diagnosis, along with outlining the possible limitations of endoscopic investigations in diagnosing a colonic malignancy.
Our patient had an impacted chicken bone in the sigmoid colon in the setting of metastatic non-small-cell lung cancer. This was investigated radiologically and found to be an intensely FDG-PET avid mass, initially presumed to be either an inflammatory mass related to the chicken bone impaction or metastatic disease related to her lung cancer. This mass appeared to resolve upon removal of the chicken bone; however, she represented later with a subacute large bowel obstruction related to the sigmoid mass which was found to be metastatic lung cancer at surgery. Consequently, our case highlights the difficulties of establishing a diagnosis in this complex case.
In this case report, we present a literature review of colonic chicken bones and investigate similar patterns across the various presentations reported. PubMed and Google Scholar were both utilised to identify the search terms "chicken bone" AND "bowel" OR "large bowel" OR "colon". The results were systematically reviewed to include only case reports of chicken bones in the large bowel, while the details of each case were analysed for the purposes of the literature review.

Case Presentation
We present the case of a 60-year-old lady who initially presented with a pseudomonas empyema and a right hilar mass. Initial diagnostic bronchoscopy revealed no endobronchial lesion. She was treated under the respiratory and infectious diseases' teams with decortication and antibiotics which resulted in marked clinical improvement. Follow-up imaging showed a persistent right hilar mass, necessitating a repeat diagnostic bronchoscopy and biopsy. This revealed a nonsmall-cell lung cancer (NSCLC) adenocarcinoma which was EGFR and ALK negative.
Baseline staging imaging revealed that she had metastatic disease with a right lung primary lesion, mediastinal nodes, and adrenal, frontal skull bone, and left pelvic bone metastases (T4N2M1c). She underwent an FDG-PET scan as part of her staging investigations in June 2017, revealing an area of intense heterogenous FDG-PET avidity in the sigmoid colon. This was suspicious for a metastatic deposit or a complication secondary to diverticular disease ( Figure 1). However, a colonoscopy done 6 months prior had been normal. A CT scan was performed which demonstrated a focal area of thickening of the sigmoid colon ( Figure 2); however, given the recent colonoscopy findings, the possibility of malignancy was deemed less likely in this situation.
The patient had minimal comorbidities and palliative systemic treatment, including radiation, was organised. She proceeded to carboplatin plus gemcitabine chemotherapy and completed 4 cycles in September 2017. She received palliative radiation to the right frontal bone and left pelvis metastatic deposits. She was then commenced on maintenance pemetrexed chemotherapy in October 2017.
In March 2018, she had a repeat colonoscopy, which revealed two polyps and evidence of diverticulosis in the sigmoid and descending colon. The polyps were removed, and histopathology revealed no evidence of malignancy.
In April 2018, she developed asymptomatic low-volume brain metastases in the left temporal, left occipital, and right posterior frontal lobes ranging from 3 mm to 16 mm in diameter. She underwent gamma knife treatment to these lesions and proceeded to Nivolumab immunotherapy in April 2018.
After 2 cycles of Nivolumab, our patient developed mild lower abdominal pain, which she complained of during her outpatient oncology visits. This had been diag-nosed as diverticulitis by her general practitioner, who commenced antibiotic treatment.
A CT scan demonstrated circumferential thickening of the bowel wall in the sigmoid colon and a suspiciouslooking intraluminal tubular structure distal to this, suspicious for a foreign body (Figures 3 and 4). The patient could  not remember ingesting anything unusual or ingesting a bone. She, also, did not have any further colonic instrumentation after her colonoscopy. There was some thought that this may have been a clip from her colonoscopy, although the appearance of the foreign body was not consistent with this. Nivolumab was ceased and antibiotics were continued.
The patient continued to eat normally during this time and reported no changes in her bowel habits. She had no fevers and the only abnormality on her blood results was a raised C-reactive protein. The clinical decision was to follow this closely with serial imaging. Progress imaging 2 weeks later confirmed persistence of this foreign body. Consequently, our patient was admitted due to ongoing lower abdominal and suprapubic pain and for intravenous antibiotics. A repeat FDG-PET-CT scan was conducted, revealing an intensely FDG avid mass in the midsigmoid colon ( Figure 5). The increase in size of the mass was concerning for a primary neoplasm or an extramural metastatic deposit from our patient's advanced lung cancer, given she had a colonoscopy which revealed no mucosal neoplasm.    Despite these findings, it was still possible that this was secondary to an inflammatory rather than a neoplastic process. The patient was scheduled for a flexible sigmoidoscopy to evaluate the intracolonic foreign body. This revealed a chicken bone impacted in the sigmoid colon ( Figure 6). The extent of the inflammation was such that the scope could not be passed 10 cm beyond the chicken bone. Nevertheless, the bone was easily removed with a snare. Imaging was conducted after 3 days to ensure there was no perforation or complication, as a result of procedure, given our patient's concomitant chemotherapy, following which she was discharged.
The patient unfortunately represented the day after discharge with a hip fracture following a mechanical fall. She underwent a hip replacement and during her postoperative recovery developed more abdominal pain. A further CT scan raised concern that this mass had become an intramural abscess with images displaying some gas locules within it ( Figure 7). She was managed with further intravenous antibiotics for 2 weeks. Progress imaging had revealed little change in the mass, and the antibiotics were ceased.
She was discharged and remained well the first week following her discharge. The following week, she developed worsening pain, fevers, and a subacute large bowel obstruction. She underwent an emergency laparotomy, at which time, she was found to have a large, fungating, and hard mass, which was densely adherent to the bladder. She underwent a resection of this sigmoid mass along with a contiguous segment of the bladder (Figure 8). The segment of the bladder was repaired, and an end colostomy was fashioned. Histopathology confirmed that this mass was a large deposit of metastatic lung cancer ( Figure 9).
Unfortunately, during the course of her recovery, our patient had another fall and broke her other hip. She has since had this hip replaced and has recovered from her surgery and is managing her stoma. She underwent further rehabilitation and was discharged home. She remains on systemic treatment for metastatic lung cancer.

Discussion
Our case represents a rare and unusual presentation of an impacted chicken bone in the setting of a sigmoid mass.  Thirty-six reports of complications as a result of chicken bones in the large bowel were identified in the English literature ( Table 1). The sigmoid colon was implicated in 22 of these 36 case reports. This is not surprising as the rectosigmoid junction represents one of the narrowest regions in the gastrointestinal tract and hence represents the more likely area where complications from ingested foreign bodies may present [3]. In our review of the 36 reported cases of complications from chicken bone ingestion, nonspecific abdominal pain was a common presenting complaint throughout, in similar fashion to how our patient presented. Radiology formed a cornerstone in the workup of patients with ingested foreign bodies, with CT and X-ray of the abdomen standing out as the most common investigations organised. Ultimately, endoscopy served as the most common means of gaining a definitive diagnosis, while concomitantly managing the condition. Surgery, however, was necessary in cases where the chicken bone had led to serious complications.
In terms of these complications from ingested chicken bones, bowel perforation was noted to occur in 19 of the 36 case reports analysed. A history of gastrointestinal disease, such as diverticulosis and colonic malignancy, predisposes individuals to experiencing complications of ingested foreign bodies, especially that of perforation [1]. In our patient, the foreign body persisted in its location in the sigmoid colon just beyond the mass and did not cause a perforation despite her known diverticulosis.
A review of the literature revealed that patients with a history of alcoholism, dentures, or sensory neuropathy are most at risk of swallowing a foreign body [2]. Our patient did have dentures, which may very well have predisposed her to accidentally ingesting a chicken bone, which at the time she could not recall.
Our patient was on an immune checkpoint inhibitor for her lung cancer. Immune checkpoint inhibitors have known immune-related gastrointestinal toxicities such as diarrhoea and colitis. Rare cases of bowel perforation requiring colostomy have been reported in the literature [38]. The development of an intramural sigmoid abscess in our patient following the chicken bone removal could be solely attributed to the chicken bone impaction and subsequent removal. It is possible that the impacted chicken bone may have affected or breached the luminal integrity of the bowel focally leading to abscess formation on its removal. Equally, hypothetically, tumour response in the metastatic lung cancer deposit in the sigmoid colon could have contributed to some degree to a breach in the colonic integrity and the formation of the intramural abscess. In our patient, both factors may have played a role in the abscess formation and ensuing colonic obstruction that necessitated surgery.
To our knowledge, this is the first case of chicken bone impaction in the setting of metastatic lung cancer to the sigmoid colon. Some of the difficulties, even with modern imaging and FDG-PET, in differentiating inflammatory from neoplastic processes in the bowel are described. This case highlights that while colonoscopy is useful in visualising the bowel from within and is crucial in diagnosing malignancies arising from the bowel mucosa, its ability in diagnosing extramural malignancies arising beyond or external to the mucosa of the bowel as in the case of metastatic extramural disease can be limited.

Conclusion
Foreign bodies mostly present with nonspecific abdominal pain, and while the majority are managed surgically, they can sometimes be retrieved endoscopically. In the large bowel, the sigmoid colon is the most common site of complications arising from ingested chicken bones. The literature review identified that perforation of the bowel tends to occur in the setting of diverticular disease and malignancy. Our case reflects the diagnostic complexity in a patient with an ingested foreign body in the setting of metastatic disease, despite modern radiological investigative modalities and endoscopy. This report highlights the value of keeping ingested foreign bodies in mind when formulating differential diagnoses for nonspecific abdominal pain. At the same time, it identifies a key area in oncological practice, where

Consent
Written and informed consent was acquired from the patient for the purposes of publication of this report, along with accompanying images. A copy of the consent form is available for review by the editor-in-chief, if required.