Fine stools and anal pain after defecation may be related to dietary factors, sinusitis, hemorrhoids and other reasons. 1. Dietary factors: if you eat too much spicy, greasy food, may cause intestinal peristalsis too fast resulting in very fine stools, after defecation due to spicy food metabolic residue stimulation, can lead to a little pain in the anus. 2. Sinusitis: Inflammatory stimulation leads to anal swelling, which can lead to thin stools and pain after defecation. 3. Hemorrhoids: If you suffer from internal and external hemorrhoids, the presence of internal hemorrhoids can make your stools thinner, and friction against external hemorrhoids during defecation can cause swelling and pain. It is recommended that patients with thin stools and a little pain in the anus after defecation go to the hospital in time to clarify the cause of the disease, and if treatment is needed, standardized treatment should be carried out under the guidance of the doctor to avoid delaying the condition.