distal to the outer catheter distal opening; and delivering a fluid through the outer catheter lumen and through at least one of: the outer catheter distal opening into the vasculature of the patient, or at least one sidewall opening of the plurality of sidewall openings into the inner catheter lumen. 

[0020] Clause 15: In some examples of the method of clause 14, the fluid is delivered through the outer catheter lumen through the at least one sidewall opening into the inner catheter lumen in response to a differential pressure between the outer catheter lumen and the inner catheter lumen being greater than or equal to a predetermined threshold value. 

[0021] Clause 16: In some examples of the method of clause 15 or clause 16, the method further comprises positioning the inner catheter distal opening proximate to a soft tissue in the vasculature; and generating a suction in the inner catheter lumen. 

[0022] Clause 17: In some examples of the method of clause 16, the inner catheter distal opening is positioned in the vasculature so that the soft tissue substantially covers the inner catheter distal opening, and the fluid is delivered through the at least one sidewall opening in response to the soft tissue substantially covering the inner catheter distal opening. 

[0023] Clause 18: In some examples of the method of any of clauses 14-17, the alignment element comprises an alignment structure extending from the inner catheter and configured to engage with a proximal end of the outer catheter. 

[0024] Clause 19: In some examples of the method of any of clauses 14-18, the alignment element comprises a plurality of markings, each marking corresponding to a predetermined position of at least one sidewall opening of the plurality of sidewall openings of the inner catheter relative to the outer catheter distal opening. 

[0025] Clause 20: In some examples of the method of any of clauses 14-19, the fluid comprises saline. 

[0026] Clause 21: In some examples, an aspiration catheter system comprises: an outer catheter defining an outer catheter lumen and an outer catheter distal opening; an inner catheter configured to be positioned within the outer catheter lumen, the inner catheter defining an inner catheter lumen, an inner catheter distal opening, and a plurality of sidewall openings proximal to the inner catheter distal opening; and an alignment element configured to indicate a predetermined position of the inner catheter relative to the outer catheter when the inner catheter is received within the outer catheter distal opening, wherein when the inner catheter is at the predetermined position, the aspiration catheter system defines: a first flow path of fluid from the outer catheter lumen through 

