Accidental formaldehyde injection during prostate biopsy: a rare cause of rectal necrosis and perforation. Case report and review of the literature

Abstract

Introduction and importance:

Accidental chemical injuries in medical settings are uncommon but can have devastating consequences. Formaldehyde (commonly in the form of formalin solution) is widely used as tissue fixative in clinics and laboratories. If inadvertently introduced into living tissue, formaldehyde causes rapid protein coagulation and tissue fixation, leading to cell death and necrosis. We present a rare case of rectal injury and perforation caused by accidental formaldehyde injection during a prostate biopsy.

Case presentation:

A 70-year-old male underwent a transrectal prostate biopsy which was complicated by the accidental injection of formaldehyde 4% into the rectum. One week later, he presented to our clinic with persistent rectal pain and was found to have an extensive rectal wall necrosis with perforation. Prompt intervention was undertaken with broad-spectrum intravenous antibiotics, transanal surgical debridement of necrotic tissue, and endoscopic vacuum therapy (EVT) to manage the rectal defect. The patient’s condition improved with each sequential sponge change over an 11-day period, leading to cavity closure and granulation. He was discharged in stable condition on postoperative day 14. Two months later the rectal wound had completely healed.

Clinical Discussion:

Accidental injection of formaldehyde into viable tissues is rare, but it can result in severe consequences. Early identification of the injury, followed by appropriate treatment (in our case, EVT), offered the best management approach and led to full recovery without the need for a diverting ostomy.

Conclusion:

This case highlights a rare iatrogenic chemical injury with formaldehyde, its successful management with minimally invasive endoscopic vacuum therapy (EVT), and underscores the need for stringent precautions to prevent such hazardous incidents.

Introduction and importance

Accidental chemical injuries in medical settings are uncommon but can have devastating consequences. Formaldehyde (commonly in the form of formalin solution) is widely used as tissue fixative in clinics and laboratories. If inadvertently introduced into living tissue, formaldehyde causes rapid protein coagulation and tissue fixation, leading to cell death and necrosis[1]. Such events are exceedingly rare; only a handful of case reports document accidental formalin injection in patients^[2–6]. We present a rare case of rectal injury and perforation caused by accidental formaldehyde injection during a prostate biopsy. The rarity of this scenario, coupled with the potential for life-threatening complications (infection, perforation, hemorrhage), makes it a noteworthy addition to the medical literature. This work has been reported in line with the SCARE criteria[7].

HIGHLIGHTS

• Rectal wall necrosis and perforation resulting from iatrogenic chemical injury are uncommon.

• Symptoms may take several days to manifest.

• Treatment should begin promptly after diagnosis.

• A minimally invasive approach utilizing endoscopic vacuum therapy is both safe and effective.

• Due to the extraluminal nature of the condition, treatment can be performed without the need for diversion ostomy.

Case presentation

A 70-year-old male with no significant medical history underwent a transrectal ultrasound-guided prostate biopsy for evaluation of elevated prostate-specific antigen (PSA). During the procedure, a syringe believed to contain local anesthetic was mistakenly filled with Formaldehyde 4 % and injected transanal into the peri-rectal tissue. The error was not immediately recognized. The patient initially had mild procedure-related discomfort but was discharged on the same day without obvious complication. One week later, the patient developed persistent, worsening rectal pain and tenesmus. He reported difficulty sitting and new-onset deep pelvic discomfort but denied fevers or significant rectal bleeding. On examination at our emergency department, he was afebrile and hemodynamically stable. However, digital rectal exam elicited severe pain. Laboratory studies showed leukocytosis (WBC 12 300/µL) and an elevated C-reactive protein (CRP) of 99 mg/L, consistent with an inflammatory response. Flexible rectoscopy was performed by the consultant surgeon and head of surgical endoscopy at our institution to evaluate the rectal pain and revealed a region of gray-black necrotic tissue on the anterior rectal wall, approximately 4–5 cm from the anal verge (Fig. 1a–b). A localized rectal perforation was evident in the center of the necrotic area, with a cavity extending extraluminally. No active bleeding was seen. The appearance was consistent with chemical injury leading to coagulative necrosis of the rectal wall. A computed tomography (CT) scan initially revealed an extraluminal cavity in the pararectal region, confirming the extent of tissue necrosis and perforation (Fig. 2a). The patient was started on broad-spectrum intravenous antibiotics (covering gram-negative and anaerobic flora) to treat and prevent sepsis from the rectal wall defect. He was taken to the operating theater for urgent transanal debridement. Under anesthesia, the operation was performed by the same surgical consultant, the necrotic rectal tissue was surgically excised down to viable margins. Given the sizable perforation and cavity, definitive repair was deferred in favor of applying an endoscopic vacuum therapy (EVT) system to promote healing. An open-pore polyurethane sponge was placed into the extraluminally defect, a continuous negative pressure (−125 mmHg) was administered. (Fig. 1c). Over the next 11 days, the patient underwent endoscopic sponge changes every 2–3 days. With each change, the cavity showed progressive reduction in size and development of healthy granulation tissue. By day 11, the defect had markedly decreased and was nearly closed. Throughout therapy, the patient’s pain improved and he tolerated a liquid diet. In total, four sponge exchanges were performed until the rectal perforation was sealed. The patient recovered without any major complications. His inflammatory markers trended down to normal by the end of the second week of hospitalization. He was discharged in stable condition on postoperative day 14. At a 2-month follow-up visit, a flexible endoscopy demonstrated complete healing of the rectal wall. Scar tissue was noted at the injury site but with no stricture or residual cavity (Fig. 1d). The patient reported normal bowel function and complete resolution of rectal pain. A follow-up CT scan showed complete resolution of the cavity (Fig. 2b).

Figure 1.

(A–D) Endoscopic images demonstrating the progression of rectal wall healing. (A–B) Initial findings of rectal wall necrosis. (C) Treatment with an open-pore polyurethane sponge for vacuum therapy. (D) Complete healing of the rectal wall defect after therapy.

Figure 2.

(A–B) CT scan findings. (A) Extraluminal cavity in the pararectal region at initial presentation. (B) Follow-up CT scan after 2 months, showing complete resolution of the cavity.

Clinical discussion

Accidental formaldehyde injection is an exceedingly rare occurrence, but documented cases across various medical fields reveal common patterns of injury and management. Formaldehyde’s mechanism of toxicity is well-established: it causes rapid coagulation of proteins, essentially “fixing” the cells and tissues in place. In living tissue, this leads to immediate cell death and a distinct type of coagulative necrosis[1]. In our case, the rectal wall necrosis progressed to perforation and risked pelvic sepsis, necessitating aggressive intervention. This case appears to be the first reported instance of formalin injection injury during a prostate biopsy resulting in rectal necrosis and perforation. However, other inadvertent formaldehyde injections have been described in the literature, each highlighting the potent tissue injury caused by this chemical. Putterman et al first reported an accidental formaldehyde injection during cosmetic blepharoplasty, which led to sloughing of eyelid tissues[2]. Yenidunya et al described similar occurrences in periocular surgery: a 71-year-old woman suffered full-thickness necrosis of both upper eyelids when formalin was mistakenly injected instead of local anesthetic during an eyelid lift. The patient developed severe ocular complications and required multiple reconstructive surgeries to restore her eyelids[3]. In the oral and maxillofacial realm, accidental formalin injections have likewise caused serious injuries. Dandriyal et al reported a case of a 35-year-old woman who, during a dental procedure, was inadvertently injected in the pterygomandibular space with 10% formalin instead of lidocaine[4]. The patient immediately experienced intense burning pain at the injection site. Despite prompt recognition and an attempted surgical debridement and drainage on the day of injury, she developed necrosis of the medial pterygoid muscle, which had to be surgically excised weeks later. Similarly, Ege et al described a 28-year-old male who received an accidental injection of formocresol (a formaldehyde-containing dental disinfectant) instead of anesthetic in the maxilla[5]. The outcome was a “tunnel-shaped” defect of the maxillary bone from osteonecrosis, along with gingival necrosis. Sarode et al performed a literature review and found only seven reported cases of inadvertent formalin injection during routine biopsy or dental procedures up to that time. They added an eighth case: a patient in whom formalin was accidentally infiltrated into the buccal mucosa during an oral biopsy. This led to chemical cellulitis of the face and mucosal necrosis that had to be managed with surgical debridement and guided healing[6].

In our case, the injury was discovered days later due to its internal location. However, the patient was informed by the treating doctor about the iatrogenic injury. The patient himself was a chemist and directly understood the possible consequences of this iatrogenic injury. As he presented to the emergency room, he was calm, asking about the possible treatments and success rates. After both clinical and endoscopic examinations, we shared with him our treatment plan which did not include a diverting ostomy. He was relieved and we proceeded with urgent debridement. Broad-spectrum antibiotics are indicated given the high risk of infection in necrotic tissue (our patient had evidence of systemic inflammation with elevated WBC and CRP). Adjunct therapies can then be tailored to the location of injury. After surgical debridement of necrotic tissues, we applied EVT – a minimal invasive approach widely used in Germany for treating anastomotic leaks and perforations in colorectal surgery^[8–10]. It promotes wound healing by continuous drainage of fluid, reduction of cavity size via negative pressure, encouraging the granulation tissue formation. The fact that the sponge was placed extraluminally allowed our patient to maintain an oral intake with subsequent normal defecation without the need for a diverting colostomy. This approach was also proven to be feasible in recent work[11]. Our case shares the common limitations of any case report, as these typically involve rare and sometimes unique events, are often retrospective in nature, and may raise ethical or medicolegal concerns – especially when the event is iatrogenic. Iatrogenic injuries are an inherent part of the medical system and, unfortunately, will always occur to some extent. Intentionally injecting formaldehyde is not only unethical and harmful, but potentially criminal. However, when such an event is classified as iatrogenic, it implies it was accidental – a mistake – because physicians are human, and humans make mistakes. In our view, such cases must be highlighted to raise awareness among medical teams, ensuring that these errors become even rarer. Once an injury is recognized, the most important step is to provide appropriate care to the patient – the “first victim” – while also offering support to the healthcare provider – the “second victim.” This dual focus helps foster a culture of learning rather than blame, promoting a safer, healthier, and more constructive clinical environment[12].

Conclusion

This case underscores the rare but severe nature of iatrogenic chemical injuries caused by formaldehyde, resulting in rectal wall necrosis. It also demonstrates the successful management of such injuries using minimally invasive EVT. It highlights the crucial importance of stringent safety measures, including careful labeling, handling of chemical solutions, and strict adherence to verification protocols to prevent similar incidents in the future.

Ethical approval

A written informed consent was obtained from the patient for publication of this case report with any accompanying images.

Consent

A written informed consent was obtained from the patient for publication of this case report with any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Sources of funding

No funding was obtained for this study.

Author contributions

I.K.: operated on the patient, and with A.A.: performed the endoscopic treatments, provided the data, and wrote the initial draft. C.S.: supervised the work and read and agreed on the initial draft.

Conflicts of interest statement

All authors declare no conflicts of interest for this manuscript.

Guarantor

Prof. C. Schafmayer, Dr. I. Kamaleddine.

Research registration unique identifying number (UIN)

None.

Provenance and peer review

Not invited paper.

Data availability statement

All available data are available upon reasonable request.

Assistance for the study

None.

Acknowledgments

AI was not involved in the preparation of this manuscript.