HAL was "built to suffer," and he expresses every bit of that suffering in excruciating detail. He's full of sensors that help him show a variety of emotions and responses. He bleeds, he cries for his mom, he urinates, and of course, he goes into anaphylactic shock. Yes, all of the major emotions, from bleeding to urination. HAL is truly representative of the full human experience.
HAL can have his pulse, blood sugar, blood oxygen, and carbon dioxide levels measured, his pupils can be dilated, and when he's left alone, he can presumably reposition himself in subtle yet deeply unsettling ways.
Medical trainees who previously complained about practice situations not being realistic enough now struggle to handle the eerie realism that HAL offers. This urinating homunculus has even brought participants to tears when the stress level was cranked up enough. Which is convenient, because HAL is clearly powered by the sound of human weeping.