The bicarbonate (HCO3−) exits at the basal portion of the cell via sodium (Na+) symport and chloride (Cl−) antiport and re-enters circulation, where it may accept a proton if blood pH decreases, thus acting as a weak, basic buffer. The remaining H+ left over from the intracellular production of carbonic acid (H2CO3) exits the apical (urinary lumen) portion of the cell by Na+ antiport, acidifying the urine. There, it may join with another bicarbonate (HCO3−) that dissociated from its H+ in the lumen of the urinary space only after exiting the proximal convoluted kidney cells/glomerulus as carbonic acid (H2CO3) because bicarbonate (HCO3−) itself can not diffuse across the cell membrane in its polar state. This will replenish carbonic acid (H2CO3) so that it then may be reabsorbed into the cell as itself or CO2 and H2O (produced via a luminal carbonic anhydrase). As a result of this whole process, there is a greater net balance of H+ in the urinary lumen than bicarbonate (HCO3−), and so this space is more acidic than physiologic pH. Thus, there is an increased likelihood that any bicarbonate (HCO3−) that was left over in the lumen diffuses back into the cell as carbonic acid, CO2, or H2O. In short, under normal conditions, the net effect of carbonic anhydrase in the urinary lumen and cells of the proximal convoluted tubule is to acidify the urine and transport bicarbonate (HCO3−) into the body.
Painful bruising syndrome (also known as "autoerythrocyte sensitization", "Gardner–Diamond syndrome", and "psychogenic purpura") is an idiopathic trauma-induced condition seen in young to middle-aged women who sometimes manifest personality disorders. : 829   It is characterized by a distinctive localized purpuric reaction occurring primarily on the legs, face and trunk, with recurring painful ecchymoses variably accompanied by syncope, nausea, vomiting, gastrointestinal and intracranial bleeding.Patients with this condition can experience frequent painful bruising around joints and muscles. Because of the rarity of the disorder, there are few methods of support in place for patients.Many patients are labelled with the stigma of having a psychological condition without this having a specifically proven link. There have been cases of painful bruising syndrome reported where there are no additional psychological disorders. This has been known to be put into remission with chemotherapy. It was characterized in 1955 by Frank Gardner and Louis Diamond.Patient may present with a history of intermittent purpura mostly precipitated by stress. See also
List of cutaneous conditions

References
Further reading
Panconesi, E., & Hautmann, G. (1995). Stress, Stigmatization and Psychosomatic Purpuras. International Angiology 14: 130–137. Yuecel, B., Kiziltan, E., & Aktan, M. (2000). Dissociative Identity Disorder Presenting With Psychogenic Purpura. Psychosomatics 41: 279–281. == External links ==