Retroperitoneal fibrosis mimicking benign disease - a paraneoplastic clue to small bowel adenocarcinoma: A case report

Table 1 Trend of inpatient labs

CMP	Admission	Day 2	Day 3	Day 4	Day 5	Day 6
BUN	20	17	14	15	14	16
Creatinine	1.26	1.2	1.42	1.46	1.38	1.24
eGFR	59	48	39	38	40	46
CBC
Hemoglobin	11.1	10	9.7	10	9.9	11.3
Hematocrit	33.4	31	30.3	30.1	31.2	36
WBC	14.42	13.84	8.29	8.15	5.93	6.48
Platelets	433	427	386	423	423	466
Immunoglobulins
IgG		407
IgG class 1		196.5
IgG class 2		131.8
IgG class 3		40.4
IgG class 4		9.4

BUN: Blood urea nitrogen; eGFR: Estimated glomerular filtration rate; CBC: Blood cell count; WBC: White blood cell; IgG: Immunoglobulin.

Table 2 Timeline of the disease

Timeframe	Clinical events
Approximately 1 year prior to admission	Unintentional weight loss (16 pounds), abdominal discomfort and UTIs
2-3 weeks prior to admission	Worsening lower abdominal pain and cramping
Few days prior to admission	Underwent right breast stereotactic biopsy for nonpalpable breast lesion
Hospitalization	Fever, chills, nausea, vomiting, abdominal discomfort, and productive cough × 2 days
	Labs: Leukocytosis with neutrophilia; abnormal urinalysis consistent with UTI
	Imaging: Retroperitoneal soft tissue infiltration, hydroureteronephrosis, lymphadenopathy, and hepatic lesions
	Management: PNT placement and supportive care
	Biopsy: Fibroinflammatory tissue consistent with retroperitoneal fibrosis
	RPF workup: IgG4 and autoimmune serologies negative
4 months after discharge	Image-guided liver biopsy due to extensive disease and hepatic lesions
Final diagnosis	Metastatic small bowel adenocarcinoma causing secondary retroperitoneal fibrosis
Treatment	Initiation of FOLFOX chemotherapy
Follow-up	Partial radiographic response of hepatic metastases; progression of symptoms and chemotherapy-related toxicity
Outcome	Transition to hospice care and subsequent death

UTI: Urinary tract infection; RPF: Retroperitoneal fibrosis; FOLFOX: Folinic acid, fluorouracil, and oxaliplatin; PNT: Percutaneous nephrostomy tubes; IgG4: Immunoglobulin G4.