Zhao Y, Wu XC. Primary renal carcinoid tumor in a horseshoe kidney presenting with constipation: A case report. World J Clin Cases 2026; 14(28): 127786 [DOI: 10.12998/wjcc.127786]
Corresponding Author of This Article
Xing-Cheng Wu, MD, Department of Urology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, No. 1 Shuaifuyuan, Dongcheng District, Beijing 100730, China. wxc_pumch@163.com
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Urology & Nephrology
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case-report
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Zhao Y, Wu XC. Primary renal carcinoid tumor in a horseshoe kidney presenting with constipation: A case report. World J Clin Cases 2026; 14(28): 127786 [DOI: 10.12998/wjcc.127786]
World J Clin Cases. Oct 26, 2026; 14(28): 127786 Published online Oct 26, 2026. doi: 10.12998/wjcc.127786
Primary renal carcinoid tumor in a horseshoe kidney presenting with constipation: A case report
Yi Zhao, Xing-Cheng Wu
Yi Zhao, Xing-Cheng Wu, Department of Urology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China
Author contributions: Zhao Y wrote the article; Wu XC provided the case and performed the operation.
AI contribution statement: The authors take full responsibility and accountability for all content of this manuscript, including any portions for which AI tools were used as assistive technologies. All AI-assisted outputs were carefully reviewed, validated, and approved by the authors. AI tools were not used to generate original scientific data, perform independent scientific analyses, or draw scientific conclusions.
Supported by Peking Union Medical College Hospital Outstanding Young Talent Development Program, No. UBJ06536.
Informed consent statement: Written informed consent was obtained from the patient for publication of this case report and any accompanying images.
Conflict-of-interest statement: All authors declare that they have no conflict of interest to disclose.
CARE Checklist (2016) statement: The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).
Corresponding author: Xing-Cheng Wu, MD, Department of Urology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, No. 1 Shuaifuyuan, Dongcheng District, Beijing 100730, China. wxc_pumch@163.com
Received: September 7, 2026 Revised: September 30, 2026 Accepted: October 22, 2026 Published online: October 26, 2026 Processing time: 46 Days and 22.6 Hours
Abstract
BACKGROUND
Primary renal carcinoid tumors (PRCTs) are rare well-differentiated neuroendocrine neoplasms of the urogenital system, though neuroendocrine tumors predominantly arise within the gastrointestinal tract. PRCTs are particularly rare, with approximately 100 cases reported since the first documented case in 1966. Horseshoe kidney represents a well-recognized congenital anatomical risk factor for PRCT. Constipation as a predominant presenting symptom of PRCT is highly atypical and has seldom been described in previous literature.
CASE SUMMARY
A 30-year-old female patient presented with a one-year history of left-lower abdominal distension and chronic constipation. Incidental imaging revealed a left-sided renal mass in a horseshoe kidney with fused lower renal poles. Computed tomography urography further characterized it as a 5.6 cm × 4.7 cm soft-tissue mass in the mid-lower portion of the left kidney containing central necrotic changes. Preoperative staging work-up, including chest computed tomography and abdominal-pelvic imaging, excluded distant metastatic lesions. Laparoscopic left radical nephrectomy was performed. Postoperative pathological examination confirmed a PRCT, pT2aN0M0. Immunohistochemistry revealed focal chromogranin-A positivity and diffuse synaptophysin and vimentin positivity. The patient’s constipation and abdominal distension completely resolved at 4 weeks after surgery. Although serum neuroendocrine marker levels were not obtained before surgery, 12-month postoperative surveillance computed tomography revealed no evidence of tumor recurrence or metastasis.
CONCLUSION
PRCTs should be included in the differential diagnosis for renal masses occurring in patients with a horseshoe kidney. Atypical gastrointestinal symptoms such as refractory constipation may represent a clinical clue for this rare neoplasm. Definitive diagnosis relies on comprehensive pathological and immunohistochemical evaluation together with the exclusion of extrarenal neuroendocrine primary lesions.
Core Tip: Primary renal carcinoid tumor (PRCT) is a rare neuroendocrine neoplasm strongly associated with a horseshoe kidney. This case describes a patient with refractory constipation as the main complaint. Clinicians should be aware of unexplained constipation in patients with a horseshoe kidney, even in the absence of hematuria or lumbago. Exclusion of extrarenal neuroendocrine origin and adequate postoperative oncologic surveillance are essential for PRCT management.
