BackgroundSolid pseudopapillary neoplasm (SPN) is a low-grade malignant tumor that occurs in 60% of all pediatric pancreas tumors. Radical tumor resection is essential; however, spleen preservation is also crucial to prevent overwhelming post-splenectomy infection. In contrast, spleen preservation is not always possible, because left-sided portal hypertension (LSPH) can cause splenic vein stenosis or occlusion induced by pancreatic tumor. We herein report on a pediatric patient of LSPH due to SPN in the pancreatic tail.Case presentationA 12-year-old girl was admitted to our hospital with left upper quadrant abdominal pain. A solid mass was palpated in the left costal region. The patient showed slight anemia (Hb: 11.8 g/dL) and elevation of inflammatory reaction (CRP: 5.98 mg/dL) without positive tumor markers. A radiological examination revealed that a 9 cm-sized mass with hemorrhagic necrosis in the pancreatic tail. Splenic venous flow was not detected and collateral draining into the left gastric vein and left renal veins were developed with splenomegaly. LSPH was involved at the time of diagnosis. The tumor was diagnosed with SPN, hence tumor resection with spleen preservation was performed. Six months after surgery, the patient developed a left quadrant abdominal pain that worsened during exercise. There was no improvement of splenic venous flow and splenomegaly. LSPH remained with splenomegaly, which possibly triggered the patient’s abdominal pain. The patient underwent splenectomy 9 months after the tumor resection. After the splenectomy, the patient’s abdominal pain disappeared without any recurrence 8-year post-surgery.ConclusionsLSPH has not been a major focus in previous SPN pediatric patients, although most symptomatic LSPH patients required splenectomy. Careful post-operative observation for LSPH is important for pediatric SPN patients.