Lupus cystitis is a rare manifestation in systemic lupus erythematosus (SLE); it usually occurs in association with gastrointestinal manifestations. We report two cases of lupus cystitis without bladder irritation symptoms. Both cases developed severe abdominal pain, nausea, and diarrhea and showed no bladder irritation symptoms. The diagnosis of lupus cystitis was made by abdominal ultrasonography and bladder biopsy. The patients were treated with intravenous methylprednisolone pulse therapy followed by oral prednisolone. Their symptoms were ameliorated, and hydroureteronephrosis improved. Thus, when a patient with SLE shows gastrointestinal symptoms, further examinations are required to determine whether the patient has lupus cystitis.