Mechanisms of Idelalisib-Associated Diarrhea in Patients With Relapsed Chronic Lymphocytic Leukemia, Indolent Non-hodgkin Lymphoma, or Small Lymphocytic Lymphoma

Inclusion Criteria: * Food and Drug Administration (FDA)-approved indications for idelalisib of relapsed, histologically confirmed B-cell indolent non-hodgkin lymphoma (iNHL) or chronic lymphocytic leukemia (CLL) * For iNHL: measureable nodal disease, defined as the presence of \>= 1 nodal lesion that measures \>= 2 cm in a single dimension as assessed by computed tomography (CT) or magnetic resonance imaging (MRI) * Discontinuation of all other therapies (including radiotherapy or chemotherapy) for the treatment of iNHL \>= 3 weeks before initiation of study treatment * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 * Absolute neutrophil count \> 750 * Platelets \> 50,000 * Total bilirubin \< 2 X institutional upper limit of normal (ULN) * Aspartate transaminase (AST) serum glutamic-oxaloacetic transaminase (SGOT)/ alanine transferase (ALT) serum glutamate pyruvate transaminase (SPGT) \< 3 X institutional ULN * Creatinine \< 2 X institutional ULN * Women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry, for the duration of study participation, and for 90 days following completion of therapy; should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately * Ability to understand and the willingness to sign a written informed consent; all patients must have signed…